For an Operations Manager multi-tenant setup I'm looking into connecting multiple SCOM environments (management groups), to our own service provider management group.

As far as I understood, data from other management group is not copied into our own SCOM database. It just uses SDK communications to retrieve the information from the different groups. 

However, I was wondering if someone has experience with this kind of setup, especially to be used in a multi-tenant environment? Are there also any hard or soft limits of how many groups you can manage from our local management group?

Hi, no known limits here, so it's mainly a hardware limits because of performance

but don't think that 10-20 connected MS can dramatically influence your local MG, as not all inf. is retrieved from connected MGs.