Response to Aaron J. Dinkin's Edits
I sort of understand about the Midland thing, but where did you get your information about /ay/ and the allophones of /ey/?  In HOVOE, which seems to be extremely reliable and pretty new, it says that /ay/ is raised to [ʌe].  I'll admit I thought that was a bit weird too, but there must have been a reason they narrowly transcribed it that way.  It doesn't say in that book that the phenomenon that's occurring in Philadelphia is exactly the same thing as what's going on in Canada, so the allophone could be slightly different than that of Canada.  It also said there was a general raising and fronting of /i/ and /eɪ/; it didn't say anything about raising and fronting only occurring before consonants.  I just want to know your sources for that information.