Los
I'm a UK approach controller, so I can't help with Airways en-route, but where radar is available, an ATC Surveillance Minimum Altitude Area Chart (ATCSMAC) is published which shows the pilot where he can be expect to be vectored and at which altitude. These levels are absolute minimums and anything lower must not be allocated. The chart is scaled and easier to use nowadays with flat screen, moving map technology.
We don't have MOCA's on our screen, but we are expected to know the ATCSMAC and mentally superimpose it on our screens (some lucky people have a map overlay they can select if needed, but it's not routinely displayed).
The minimum altitude is based on a survey of the obstacles in the area combined with a more precise knowledge of the aircraft's position because of surveillance equipment, rather than in a non-surveillance environment, so the minimum levels will almost inevitably be lower than the general MOSA for a 25 n.m radius of the airfield, or the MOSA either side of an airway centreline.
All ATCO's should be aware of the risk of terrain, and not allocate levels until they are safe...this includes levels which are unsafe in your present location, but will be safe at your next waypoint---you just DON'T do it!!
Can't point you to the ICAO doc, but the ATCSMAC was re-drawn to comply with ICAO standards about 3 years ago, so there must be something out there somewhere!
Hope this helps
Tori