Only ONE at a time. I think they can both be paired but I believe only one at a time can actually do bridging.
But now I'm not sure. Oh, wait, I am sure - YOU CAN. Since I've done it but on the bbphone (9930), it says in fewer words "your 32gig is disabled" "your 64gig is CONNECTED."
Confirmed. We do this all the time.
One 9900 can bridge to one PB at a time
You only have to make the bridge paring setup one time and 'save'
Go to bridge options on the PB and 9900 to switch/disconnect
By default, the last combo connected is the auto bridge