As far as I know, the various versions of BES are not SRP or CAL-specific for their respective versions. Personally, we've been using the same SRP since 3.6.0 and now on 4.1.0. It won't be able to run 4.0 and 4.1 at the same time, though, as it'd lock out the SRP on RIM's side. I'm not sure on the unlocking of a trial version, though. As far as the CALs, I do know that a 3.6 CAL will work on a 4.1 installation, but I'm not sure if the same logic could be placed on the SME/SBE version.
Here are some articles from RIM's KB that appear to have conflicting stories (one says simply update the CAL, the other says that you need to install the production version - both say they are applicable to 4.1).
http://www.blackberry.com/knowledgec...nodeid=1207050
http://www.blackberry.com/knowledgec...nodeid=1050086