No, all of the power line connections need to be on the same circuit. If, maybe, there is new tech out there to get around this (although I don't see how they can), you can get the latest info from the vendor of whatever product you got.
For an idea, which at least in my head looks to be sound, are the two buildings close enough for WiFi to reach from one to the other? You can setup a powerline network in one, then stick a WiFi AP on that network, another WiFi AP in the other building and get the network signal to that second building without the powerline network over WiFi from the one with it.