I started a thread: Open source CANbus alternative/pubsub over uart/message passing project - #3 by system - Networking, Protocols, and Devices - Arduino Forum about a very closely related thing.
Yes, you definitely can do this. I did this at a distance of 50 feet, using cheap headphone cable from monoprice, using the a 20k internal pull up, using 3.3v, but one of the devices was actually 5v...
I used shottky diodes though, and I seem to remember the whole thing failing with any other kind of diode. I also used a protocol that had checksums and could detect when another node tried to talk over it and stop and retry and all that stuff.