I've just been down this dark ally be there was bright light a the end.
We have an main building that connects two other building over Cisco 350 Series Bridges. I can't remember what type of Cisco antenna the bridges are connected to. They are yeaggi (spelling??) bridges. The main building has two bridges and the other buidling have a single bridge with a antenna pointing to the main building.
One building is about 20 meters away from the main building, the other is about 100 meters, with a tree in the middle.
We have Inter-Tel Axxess system with IP phones in the smaller buildings.
It took a lot of time to get the network configuration stable enough but we managed it by having one root bridge in the main building, and one of the smaller building having another root bridge.
It's been running for about 2 weeks without any problems/ complaints.