I've seen a lot of ants foraging around each other, and even nesting right next to each other. A lot of the time they meet, and do like you described--just touch antennae, and then go their separate ways. I also have a free-range (not intentionally) colony of Crematogaster in my ant cabinet, where they forage around and get into everything, and so far, I haven't seen any problems with them wandering into any other ants' nest. I think if you don't mind losing a colony or two, then it might be worth a try. I was actually going to try something like this just to see how much of what everybody assumes would happen actually happens. I think some species might not have too much of a problem foraging in the same area if their preferences are a little different like you say your ants' preferences are. Also, I would try this with a very large out world, something much larger than a 10 gallon tank. I think the biggest threat, is one colony raiding the nest of another, but I think if you have the right species this might not happen.
Basically, I would only consider this an experiment, not a recommended way to house your ants, especially if you really value the colonies.