You need to check frequently calendars of multiple group of different people.
Here is a way to do it:
1. Login into your mailbox and click on the system Calendar folder.
2. Create as example two sub-calendar folders, Multi-User1 and Multi-User2.
3. Click on Multi-User1 calendar folder and then on a right site Multi-User Columns -> Add or remove Users. Here add in a proxy list first group of users.
4. Repeat the same process for Multi-User2 calendar sub-folder to assign a second group of proxy users being displayed in the MU Calendar view.
Note, if you would do it as following:
1. Click on your system Calendar folder.
2. Right-click on Multi-User Columns -> Properties and from this dialog window you would create Multi-User1 and Multi-User2 views.
3. This would end up in a situation when a proxy user list of the last edited MU Calendar will overwrite all existing MU calendar proxy list. In other words, all MU Calendars would show the same list of proxy users.