As long as the disconnect for each apartment is accessible to each tenant, I don't see a problem but if this is locked up and they don't have a key, it would be troubling to me.
I would certainly have mis-givings about a situation like that as well.
See, over here a Main switch is defined as the switch that gives a consumer the greatest degree of control over the supply to their installation.
Now, if you need to have to switch your power off in a hurry, you don't really want to be looking around for the main switch and most non-electrical people would in fact assume that it was in the panel in their apartment, that could end in tears.
I've always been of the idea that the main switch should be installed in the same "building compartment" as the actual installation.
I mean, if you had a house, you wouldn't put your main switch out on the front fence, would you? (or would you??)
Just my $0.02 worth