It was mentioned before that Exchange 2007 SP2 contained Exchange 2010 schema completely back ported to it, but if you check the LDF files that generate the schema you may notice that they are in fact different.
Back porting the schema was not a straight forward action code wise. In order to do it, we had to add some of the properties that were in a separated file in Exchange 2010 to all the *99.ldf files in Exchange 2007 SP2. This is why you may notice that there are differences in the files that generate the schemas in between the 2 versions.
However, this change has no impact on what happens when you install E2007 SP2. Schema versions are synchronized and after installing it, the schema in your environment will be that of Exchange 2010.
- Mario Trigueros Solorio