I think it's just a matter of the DJs at the events catching on to the team names. If it hasn't been mentioned earlier, at the regionals, on Thursday just a random collection of songs are played, and no actual DJ is there. Friday and Saturday have a live DJ - usually can be found on the field side of the curtain opposite the end with the production staff. Most will let you request songs. I know last year we requested MC Hammer's "You can't touch this" in honor of our robot "hammertime". The guy actually told us that he couldn't play it during our match, but he would when we were loading the bot onto the field.
This year, the same DJ was used for LA and SD regionals, so most of the songs had a "rerun" feeling to them. I know in LA they played "if I only had a heart" in honor of 399's robot "The Tin Man". There were a few other instances of this happening, but that was the only one I actually remember.
I have been really disappointed in the fact that
Sirius has NOT been played at the CA regionals (at least Sac, LA and SD - I can't speak for SVR) ever since Jason Morrella stepped down from FRC Regional Director on the West Coast. For those of you who haven't heard it, I highly recommend
checking it out. One of the strongest memories I have from my first few years in FRC was hearing this during the team introductions in the finals and on the first matches of the day.