Generally mscorlib stuff won't work, though precisely why that's the case is not something I can speak to. I'd guess it's because Typemock Isolator itself is a .NET library and if you were mocking things you needed to use... well, I could see how that could get problematic.
I played around with mocking Console.WriteLine, and while I can mock the call - so nothing gets written to the console - I see that the FailWhenCalled expectation generates a slightly misleading message. It doesn't have anything to do with the Console.WriteLine so much as the test framework I'm using having attached to the console output:
Demo.Class1.MyTest : TypeMock.VerifyException :
TypeMock Verification: Unexpected Call to NUnit.Core.EventListenerTextWriter.
WriteLine()
at TypeMock.MockManager.a(String A_0, String A_1, Object A_2, Object A_3, Boolean A_4, Object[] A_5)
at TypeMock.InternalMockManager.getReturn(Object that, String typeName, String methodName, Object methodParameters, Boolean isInjected, Object p1)
at NUnit.Core.EventListenerTextWriter.WriteLine(String aString)
at System.IO.TextWriter.SyncTextWriter.WriteLine(String value)
at System.Console.WriteLine(String value)
Of course, technically it IS failing when the method is called, so you're getting what you want... even if the error message is a little misleading.
A simple workaround to make things cleaner around this would be to do a slight redesign so you have a "Log" method that does all of the logging in your class and have the Console.WriteLine in there. Then you could fail when your "Log" method is called rather than failing when Console.WriteLine is called.
The TypeMock folks sometimes are able to chime in with a feature that's already there but you never knew existed - maybe they'll have some additonal info here.