Hi DFC,
In the LTMA the requirements to cross points "at" or "Above" on the SIDS is for traffic and route deconfliction when the aircraft are not being provided with radar separation. They are not for terrain clearance unlike some SIDS in parts of Europe. When a controller is providing Radar Control Service, the controller is responsible for ensuring terrain separation. Therefore when a controller clears you to a level off a SID, the controller accepts responsibility for ensuring that the aircraft a) remains clear of traffic conflictions, b) remains clear of terrain conflictions.
If an aircraft reduced its climb rate such that either condition may become possible, the controller is duty bound to take action to resolve the problem
