Sounds like jibberish, but let me take a stab at it.
A lot of the expressions in Finnegan's wake (and even Ulysses) resemble the "nonsense speech" of psychotics or drunks who say whatever come into their minds. It may be possible to make sense of this jibberish, but to do so you need to decipher what's going on in the speaker's mind.
No offense, but this isn't necessarily true. While some of the language may seem to be gibberish and indicative of psychotic uninhibited speech, I assure you that Joyce's text is anything but. Almost every word stems from a highly structured and extremely conscious system of symbols and references. A surface level deciphering of the line can be attained through such an approach, but it doesn't really get to the fulls multi-level meanings that Joyce plants in the language.
This is not an easy task. I've had a chance, through my work as a neurologist, to listen to the speech of plenty of psychotic and neurologically impaired patients.
These folks often use language that makes little sense, though you can "see through" what they are saying to get at "what they mean." Often they use things like "rhyme" or "clanging" sounds, rather than "logical" associations, or what could probably be described as "subconscious" associations (e.g "stream of consciousness").
I think that you're referring to onomatopoeia here. Much of the earliest languages, it is believed, consisted of words that sounded like actions or sound associations with actions. Since language, essentially, is arbitrary and unreliable, sound recognition served as a logical means of assigning word associations. Given Joyce's vast knowledge of languages, he could speak roughly 9 nine languages and was familiar with several dialects of some of them. Much of his text consists of plays on these languages, partial transcriptions between languages, and sound associations to words and ideas. On top of that, many of the words operate on several levels. In this case, for example, "Phoenix" serves at least two purposes: 1. the mythical bird that is a symbol of regeneration and rebirth 2. the public park in Dublin where nationalists murdered a British dignitary. While seemingly separate ideas, these two concepts can actually begin to overlap and mingle in regard to meaning. The murder in Phoenix Park brought about a public scandal that ruined, in the simplest terms, the career of Irish politician, Charles Stewart Parnell. Parnell symbolized, for many, the possible rebirth of the Irish state, and many, including Joyce's father and, subsequently, Stephen Dedalus's father, a real possibility for an Irish free state. When Parnell was disgraced, through an alleged association with the Phoenix Park murders and an adultry scandal, many believed that hope for the Irish state had been lost. However, the events that occurred as a result of the 1882 event, also the same year Joyce was born, spurred a resurgence of nationalist sentiment, which ultimately led to the 1916 Easter Rising and the consequent Irish Civil War.
Also, in regard to "stream of consciousness" writing, it is not really tied to subconscious reaction. Stream of consciousness allows the reader insight into the formative mental responses and inspirations for the action and speech of the novel. A character can respond to or inspire narrative or action by mentally working through his/her mental responses to what is occurring or being said around him/her. These responses seem to be "gibberish" because we don't think as a linear narrative; we mentally respond to stimuli and, in turn, these response spur similar and sometimes seemingly arbitrary mental responses. Thus, we, as readers, only get a loose framework of rapid responses to what we see as a single stimulus. The rest of the responses are chained together by the extremely conscious reactions that the narrator has to the initial stimulus and his/her response=stimulus>response=stimulus>response=stumu lus>response, etc. "Stream of consciousness" cannot be subconscious thought, or it would be impossible to convey in text/narrative. The character has to be aware of the thoughts and connections that he/she is having/making, or they would not exist in the text that the reader is reading. And definitely don't make the assumption that Joyce was not "hyper-aware" of the connections he was putting into his text.
I've no idea what this quoted statement means...let's look at it:
"
Here in Moicane we flop on the seamy side, but up n'ent, prospector, you sprout all your worth and you woof your wings, so if you want to be Phoenixed, come and be parked."
In Moicane [wherever that is] we [and I mean regular down-to-earth folks like me, not highfalutin arrogant a-holes like you, Mr. Prospector] "flop on the seamy side" [which means we regular blokes get down and hang loose, doing what comes naturally in Moicane...wherever that is]...But you [because you are the highfalutin fellow you are] just fluff up your wings [to display your superiority]. You somehow want to rise out of this Moicane environment as a transcendent Phoenix, but you can't do that without getting low down and dirty.