Scrimshaw, as you mentioned that Nohavica's song and the word "gu" - it's not correct, not even in the dialect. The sentence you've written is "Pendolino stoji kdesyk u Polomi." - the extra sound (k) is part of "kdesi" not of "u". The people from the Ostrava region add a k at the end of words "kdosi", "cosi", "kdysi", "jaksi" and so on, it sounded like a g in that song because of assimilation of "voicedness" (don't know the proper term). The dialect also makes difference in pronunciation between i and y (that's why I spelled kdesik as kdesyk) but use the two in a way completely different from the standard czech orthography (for example "řiť" (arse) is pronounced "řyť" no matter that there's a y following a ř). This is not normally used in writing but you can tell the difference when you hear someone speak. Someone posted this before but you can take a look at ostravak.bloguje.cz to see that dialect in practice.