Can I play a Bus is Full card against another Bus is Full card?

Yes, you can!

For example, if an opponent plays a Bomb Squad card to take your full set, you could play a Bus is Full card to block them. If they play another Bus is Full card, you can play yours again to cancel their move. The opponent will then have to give you the full set. And don’t forget—Bus is Full cards don’t count as one of your three turns.