The anser is totally site specific and depends on how your storage administrators have defined the migration level mediatypes.
I have worked in shops where
a) There was no DASD migration, everything went straight to ML2 on tape
b) Where the ML2 was defined as DASD along with ML1.
So, to be pretty sure, you need to talk to your storage admin people to find out how the HSM subsystem has been defined.