Just tried to do remote-triggering of some jobs to see whether we can make use of post-receive hooks in our git repositories to trigger our build jobs.
However, jenkins did only recognize jobs where git plugin was 'directly' used without using the multiple SCMs plugin.

Any jobs using git plugin within a multiple scms configuration are not found:
Using "curl '<jenkins url>/git/notifyCommit?url=<repository url>'" we just get (for repositories which are only used within multiple SCMs plugin):
No git jobs using repository: <repository url>

For repositories which are used as well with the stand-alone git plugin we get:
"Scheduled polling of <repository name>"
However any job where <repository name> is used in multiple SCMs config is missing here as well.

Hope it's not too complicated to fix this issue...