Rudedog, it was on a standard public server: jolt.co.uk (03)TDM Realism[CKR]
It must have taken them a while to do that (If indeed they climbed on top of one another) because you have to climb 2 walls in total to get up to where that guy was.
I'm not surprised to see this sort of thing... I've seen people running across roof-tops in places a n00b like me wouldn't expect. For instance, and I'm sure some of you know about this, but in S.France I saw a guy running across the roof top in the garden-type area. I stayed away from that area for the rest of the duration, but later I had to really wonder about it. I still haven't figured it out totally (haven't really thought about it much lately either).