I created a similar filter and updated the operator record of a user adding the Security Group ID to the Security Groups list. The example query is attached.
At their next login, the mandanten filter was applied, HOWEVER, there were problems with views with groupings:
For example, for the two assignment groups the user should see, the groups were listed in the "All Open incidents" view, but the record count was incorrect, showing 0. In webtier, the user could expand and still see the tickets assigned to the group. In the Windows client, the user could not expand the groups. (DEFECT--see attached screen capture)
However, if the user selected the view "Open Incidents assigned to my group", the records displayed correctly.
Also, if the user searched for Incidents, the Mandanten filter was correctly applied, and records were displayed correctly.
There appears to be a defect with the Views grouping function as it relates to mandanten. I have not had a chance to look at the HP support site to see if there is a QCCR.