Low confidence, because normally I'd expect the montaż to be the get-in. This is when the scenery and so forth is brought to the stage area/performance space and set up, in whatever forms(s) that might take (flats, backdrops, anything that will be flown, scentery on trucks, rostra, furniture, etc. etc.). But this isn't normally a 'rehearsal' and your text very clearly says 'technical rehearsals', before listing what they are.

Hence the suggestion that it may also mean the rehearsals the crew will have for carrying out the set changes, in whatever form they might take (flying, trucking, revolve, lift-and-hump (my own expression), etc. etc.), which would most probably be carried out before the first full technical rehearsals (with lights, sound, props, actors et al.)

But it might be worth asking the client for clarification.

I hope that helps