For all practical purposes, the BCM is built around the MICS telephony components with additional IP and networking features. I'm confident that if it will work with the latest release of MICS software, It will work with the BCM though we don't have any active BCMs with old digital sets. I think there is a software cutoff point on the older IP sets without upgrading the firmware of the set but I don't recall what that is. I'll be putting my confidence to the test shortly because we'll be installing a 3.7 BCM 400 around older digital sets.
You could call 800-4nortel, express routing code 338 to verify.
We have a customer that has a 6.1 MICS, and has some 15 year old 7208s and 7310. I ran across the BSF problem there but everything else works fine, including the 7324s and CAPs.