Replacing SRAM Red chain set with Ultegra - bottom bracket? I have a cyclocross bike with an Ultegra 6700 chainset and a road bike with SRAM Red. I'm looking to get a Stages Ultegra power meter (left crank arm mounted) that I can swap between both bikes. This means I'm thinking of changing the Red chainset over to Ultegra 6700 (or Dura Ace) since the left crank arms aren't compatible.

The bike in question is a 2011 Scott Addict R15: www.bikes.org.uk/scott-addict-r15-2011-road-bike

It's listed as having a SRAM Integrated BB Press Fit but after doing some research I can't figure out whether the bottom bracket will be compatible with the Shimano chainset or not. If I have to get a new BB then that's fine, provided that the frame will accommodate it of course.

Any help or advice would be greatly appreciated, even just helping me identify exactly what BB I already have.

The other option of course would be to put a SRAM Force chainset on the cyclocross bike, if for some reason doing the conversion this way round is any easier.
You'll need a Shimano PressFit BB, to go with Shimao cranks.
Shimano and SRAM just don't share the same spindle specs. It won't cost you much however, compared to the price of the crankset.
If you don't have the dedicated tools at hand, go to your LBS and make them work.