Please ensure you apply the latest system update to BCM 4.0 before running the DMM (Data Migration Manager) tool, to collect the data off the BCM 4.0. And then once upgraded the hardware, apply the latest system update to the 450 hardware BEFORE running DMM again to copy the data back onto the BCM.
If you don't, I guarantee you'll be reconfiguring a lot of your telephony.
Also when extracting the data off the BCM 4.0, remember to save the output as a .xcm file...refer to the DMM user guide, as well as just the upgrade guide.
I made the mistake of following just the upgrade guide, and not referring to the DMM guide, so the upgrade did not go well. I also raised a case into Avaya to have the upgrade guide updated to reflect missing things like apply the latest system update.
Finally anything that says it's optional in the DMM guide, read as recommended. For example, if you just collect the data off the 4.0, without saving it as a .xcm file, you won't be able to run the import of data back onto the BCM a 2nd time.
regards
paul