YES!
Leica says that the Elmar-M can safely be collapsed in the M9, and I have been collapsing mine without any problem.
So I compared the Elmar-M and the Summitar (SM, with an M ring). The diameter of the inner end of both lens tubes seems to be the same. The collapsed Summitar does not penetrate as deeply into the body as the Elmar-M. So I tried it, and the M9 came through unscated!
So, yes, the Summitar can be collapsed safely into the M9. Of course, always mount and dismount all collapsible lenses extended.
Guy