I just watched the Italy-Holland game of the women's World Cup on ARD. The commentator, Stephanie Baczyk from Hannover, said Viertelfinale with what to my ears sounded like /ʏ/ so that it was more like /'fʏrtəlfina:lə/. Did I just mishear or is there a possible rounding of /ɪ/ in certain environments or with some speakers?
Your ears are ok. There are some regions in Germany where people speak [ʏ] (»ü«) where they should speak [ɪ] (»i«). In this regions words like »Tisch« or »Fisch« are spoken like »Tüsch« or »Füsch«, and so also »Viertel« becomes »Fürtel«.
As far as I can say, this only happens to the darker [ɪ]-sound like in the given examples, but not to the brighter [i]-sound that you most often find as a long vowel. ([ɪ] is always short, even in »Viertel«, although it's spelling indicates a long vowel.) If my hypothesis is true, then »Miete« [ˈmiːtə] will be left unchanged, while »Mitte« [ˈmɪtə] should sound like »Mütte« [ˈmʏtə].
I do not live in such an area, so its hard for me to tell if this is true or not, but i'm shure, there will be some comments about this hypothesis.
Just to make it clear: The first vowel in the word »vier« is long: [fiːɐ̯]. But the vowel in »Viertel« is short: [ˈfɪʁtl̩]. (Funny enough, »vier« has two spoken vowels ([i] and [ɐ]) while »Viertel« contains only one spoken vowel ([ɪ]).