I really don't think locators are random. If you think about it, if it is random, then it can repeat, which we know does not happen. I don't think the algorithm would say generate something randomly and then check for duplication, etc.

I would guess in the best case, it would be "random within a set of rules".

Note also that some airlines share the same system and some GDS are also used by airlines for internal reservation processing (e.g. SABRE and AA).