According to ESRB rating’s description of Bad Company 2 seems to include World War 2 levels, like the ones present in Battlefield 1943. Here’s what the ESRB certificate said, in part:

“…players conduct missions on an unnamed Japanese island during World War II and then move into the modern day.”

Since ESRB gets to review the complete and final game, it’s quite possible that we’ll see one or more maps imported from Battlefield 1943 — BC2 already has several of the weapons available from BF 1943. You can read the full ratings description here.