I have come across a few of these counterbalanced ladders in older buildings over the years. If they are structurally sound, if they are only for a few staff, if all the relevant staff have received training, have practised using them and are confident that they know how to use them in an emergency, if they are safe to use, if they have suitable lighting, if their use does not create a hazard and if they are maintained in good working order then they could be acceptable.
The onus is on the occupier to demonstrate that the above list is satisfied. Standards have changed over recent years and what used to be considered 'safe to use' might no longer be viewed in the same way.
As for obstructing other buildings' means of escape, of course it might not be an issue if those buildings are never likely to evacuate at the same time but, then again, it might be an issue.
I saw one ladder that went up from a basement and involved opening a large man hole type cover from below (ok if a motorbike wasn't parked on it). It was ok for getting out but when you saw it in its working position you noticed that a large unprotected hole in the pavement resulted from its deployment. If they want to use one of these then they should give you a demonstration of the staff using it (stress that liability rests with them).
I've seen Davy escapes where the rope hasn't been unreeled for a century, canvas chutes that were so moth eaten you'd fall straight through them and I went one place that had an escape onto a flat roof with a small, 30cm high parapet round the edge. And to get off the flat roof (and this was for members of the public, mind) there was a roof ladder lying on the roof. I dangled it from the parapet and it didn't even reach the ground! I was in a good mood that day so I said it was fine.