Heya SandVoss,
I've done this with a mission (minus the objects.. but that shouldn't be much different than placing units randomly)
Basically, I covered a town with about 30 small markers, mainly on streets and a few more open areas. Then I would have a script randomly choose a marker, and it would move group A there, then it would run again, placing group B, etc, etc... If you want a little more randomness, you could getmarkerpos, and add a random radius of say 200m... I also used this to place their waypoints... worst part about making a public map is 'knowing' what's gonna happen, and when. This kinda solved it for me.
If you want a copy of my map, I'll shoot one over to you with an explaination of which scripts do what.
Nigel.