Are special encounter locations pre-determined

I remember in Fallout Tactics, once you found a special encounter in a map square, it was possible to find up to 3 or so more in the same map square because the map locations that spawned special encounters were pre-determined each game.

Does Fallout 2 work the same way? Now that I've found the dirty bridgekeeper in his dirty robe encounter, can I run back and forth over that square to find more, or will they be purely random as I travel? (maybe with some luck stat, outdoorsman skill, and perks figured in)