Outposts

I played a multi-player match today with some friends and found that they couldn't get into my Outpost's trench network, but they COULD reinforce from it. Is this intentional? Or a bug?

Thats propably intentional since Outpost is considered as a building...f.e. if you play WM or US your teammate cannot enter the building which you have upgraded to forward base as well.

Your building, you units.