Back to the original question... for me it almost always takes a lot less then 15 minutes on hotel bids. Rejected bids usually process in about 2 minutes. Accepted bids take longer, maybe 10 minutes. My accepted bids definitely take longer to come back, to the extent that if an answer doesn't come back after 5-6 minutes I assume I was accepted.
On accepted bids there is definitely some communication between PL and the hotel. This must be so, because all accepted bids get a confirmation number from the actual hotel. Moreover, for some chains (e.g., Marriott) you can go right to the hotel's site and see your reservation by entering your confirmation number seconds after your bid is accepted.