In the very large organisation I'm working in, schema changes are handled by another department - and the servers are provisioned to the exchange team by the server team (ye another department)- with all patches and Exchange pre-reqs installed. So essentially our team does not apply the schema change nor the AD schema /Domain prep.
As you can probably guess- this falls down frequently. I'm racking my brain for a simple script to check that the schema has been extended and domain prepared. The filter pack and UCMA is easily checked.