You can use the 'Team - Per Area' filter to allow employees from vendor teams to see service requests of internal teams in the same area, while employees from internal team can see service requests of any internal or vendor team in the same area.
Note Subscription to the Area Support feature is required.
To set the Team - Per Area filter
On the Service Requests screen, tap Search, and then on the Search screen, tap Team - Per Area, and then tap Save.