Well I think ALC BACnet and Modbus integration is pretty easy. Programs are easily recycled and there's a moderately active community between dealers plus a bit of a library. There is also a tool to discover points and turn that into a program stub as well. Hardest part is knowing the protocols and sequence of operation.
Other languages are where ALC falls down. There are no reverse engineered drivers and the drivers they do have like Lon are a PITA to use. So there we look to someone like Intesis or tridium, a jace running say maxline comm4 and pumping those points out to BACnet point export works very well with ALC right down to simple point naming and getting points mapped quickly in both devices.