I was of the opinion that emergency services were aware of traffic orders, and would,know access ability and restriction before any event requiring their attendance.
With blues and twos, their rate of access wouldn’t likely be hindered much diverting around ‘the blocks’ to the correct location on the 1st occasion. (I.e. not driving along one road, only to find it was blocked and further progress impossible).
I believe they walk the LTN to assure themselves that access was sufficient for all properties.