The examples and documentation sort of suggests that it is supported, but none of my attempts to get it working are fruitful.
Looking at the code the check to see if a field is of type "enum" is simply a check for the type "enum" which does not exists in MSSQL. You would have to check for something along the lines of ... CHECK(... IN ('A', 'B')).
If my assumptions are correct I would gladly take a stab at fixing this when time permits.