Well that was unexpected! I thought ZZ Top's fill-in bassist was gonna take over Dusty's vocal parts live from now on, but it seems like Billy's just going ahead and singing them on top of his own songs. Lots of G4s in this rendition of "Tush", as well as probably some of Billy's strongest B♭4s to date!
Damn, that's a cool find! Of course the audio has to be extra trash for this one... Life's absurd humour.
Edit: lip synced?? Is that for real or is this just a rumour? Sounds a little strange to me unless someone can truly confirm this.