Can I use multiple source control providers at the same time in Visual Studio? Global switch is not enough for my needs (I have one project in SVN, another one in TFS etc.)
Yes, it can be done. You probably don't want to use multiple source code tools in the same solution (that just seems confusing), but it is possible for two systems to co-exist.
I'm a little less certain whether you can multiple source control plugins at the same time. For example, Visual Source Safe, TFS, and Ankh (I've never tried Visual Studio with any of those combinations). I'm currently working with both Visual Source Safe and Subversion, but while VSS functions specifically as a source control provider, VisualSVN which shows up as a more general add-on.
EDIT: Based on the back and forth in the comments.
Can multiple SCCM tools co-exist in Visual Studio as side-by-side installations? Yes.
Can they be used in the same solution? I've never tried it.
VS source control providers are per solution (each VS instance can use its SCP), not per project it seems.