Maariv with a mincha minyan
I'm not fully finished with my hypothetical but it goes something like this:
If I davened mincha at the earliest possible time, I can daven maariv before sunset.
If I am called to help out with a mincha minyan that is meeting a little before sunset, can I daven maariv (let's assume, without judgment, that they say Ashrei really slowly and I can say sh'ma quickly, so we would all hit kaddish and shmoneh hesrei at the same time)?
Would this be considered davening maariv "with a minyan" for me? (whether or not there are any consequences to that is not my focus -- I just want to know if one can daven a "different" prayer service which is textually identical, and get credit for being with a minyan)
Now that I think about it, the opposite case would be easier to imagine. Someone who hasn't yet davened mincha standing in with a group already davening maariv -- can he daven "with" them and consider himself as having davened mincha with a minyan?