None of the storage servers should have been storing the user data on the same volume as the OS the way a client machine would. So the network-mounted home directories should be intact and ready to use once the server OS is reinstalled. And while I don't know how SCCM works, I'd be surprised if this image push was affecting anything other than the primary physical drive (a wipe-all, populate-one recipe would be too obviously wrong and dangerous, right?).