I missed the broadcast, due to other commitments. I've not noticed any pronunciations of "bus" as "boss" hereabouts, but "block" certainly has always had an "a" sound to it.

The shift I've noticed is in "un". Often, when listening to someone on TV or radio, I hear what sounds to me like "on" being said instead. Because the persons speaking can't be fixed as to origination, I can't tell if this is a regional variation, or what. (heh - "whut")