The best method to determine what works as far as chainline is to simply try it. It is not possible to exactly determine ahead time exactly what will happen with any particular change. Having acceptable chainline simply means having acceptable shifting. Many bikes are off either way (front rings too far out or in) and yet still shift for their riders. With the newer 10 speed bikes with the shorter chainstays, it is often impossible to have every gear combination useable.
As you alreay own the bb, simply install the triple and see if it clears the frame. If the front derailleur will get the chain down there, it may be useable. Front derailleurs do have limits, however, on how for inward they will move.
See also
Chainline