Build server configuration

We want to upgrade our build servers to run our typemock tests, but I'm having a bit of trouble getting it configured correctly and finding the correct information regarding this. Our setup is a TFS2010, with 20+ projects each running from TypeMock 5.x to 6.2.2. All build definitions are msbuild based, since we are waiting to get TypeMock working with our workflow template (that besides the scope of this post). Now, I have installed Isolator 7.0 on the build servers, but I cannot seem to figure our how to make typemock work. Various questions I have.

1. Since TypeMock is installed on the build servers, I would expect that I didn't have to add any additional assemblies to source control and reference them. But it doesn't seem that the assemblies are in the GAC - Why not.
2. Since TypeMock is installed, I would expect that I didn't need to call the register (or publish for that matter) target in msbuild with licensing information - Is this correct?
3. I need to support various version of TypeMock from 5.x to 6.2.2, but have installed 7.0 on the build server. Do I need any version specific assemblies in source control pr. project and which?
4. What is the recommended way of using typemock with msbuild team build def's, when we have 7.0 on the server and 6.2.2 on the clients - what to install and where, assemblies in source control or not etc.

I've read all the documentation on this site, but still can't get this configured correctly. Regarding q3, I've now included typemock.dll, arrangeactassert.dll and configuration.dll to source control, however mstest failes without further description (TF270015: 'MSTest.exe' returned an unexpected exit code. Expected '0'; actual '-1')
Any help is greatly appreciated!