As far as camel backs go, bare this in mind, they aren't standard issue... which means, at least for courses, planning has to be done making the assumption that no one has a camel back, rather, has the standard single 1 Quart canteen... so there will be no need for a camel back...
Example, I remember a few lads on my QL3, thinking they were rather smart, buying camel backs and wearing them for the duration of the field ex... which on the surface, in 40+degrees of a damp kingston summer, seemed smart... except that they were never more then 50 feet from their truck, and there were 3 water jerries aboard said truck, so they were lugging around an extra 2-3Kg for no reason...
Like I said, if you don't know, you don't need it...