Can I use just one Google Voice number/account to place and receive calls on both lines?
Ideally, if GV supports this, my caller ID would show the same number regardless which line I dialed out from. Similarly, if one line was in use when a call came in, the other line would ring. Again, no intrinsic need for more than one number.
Is this supported by the OBi202/Google Voice/Google Talk?
If by 2 lines you mean 2 phone lines can dial out or receive calls with one number, then yes. If you needed to place and receive separate calls simultaneously, then you would need two GV accounts.