I had Evo's and CAAD's of a similar year, and are two options for what you found/what you need to go shimano BB:

1. BB30 - your bike has a built in ring/feature on each side of the BB shell that stops the bearings at the correct depth.
Solution: you can easily get a press in tube that will allow you to use a shimano BB.
ask your LBS about it, you could find the part on your own, but should have them install it with the correct tools and method.
Once the conversion tube is installed, you can install a Shimano BB and crank

2. PF30 (as the other poster mentioned) - each bearing in your BB was contained in a plastic shell
Solution: get a BB from a company (like wheels manufacturing) that makes a BB for your frame and the kind crank you want to run.
Install the BB and Install the crank

If you can't determine what you have, your LBS could tell you with a glance.