The following info may or may not be useful. Also remember that each airline implements it differently, and there is a difference between their own res system and the GDS's like Amadeus. There seem to be 3 kinds of POS:

1. ticket POS (associated with the original ticket number).
2. reissue POS (associated with the reissued ticket number).
3. computer terminal "POS" (associated with the network address of the computer making the inquiry).

At various times one of these 3 seem to be used, and it varies by airline and transaction. I suspect the intent is to always use 1 for ticketing, and 3 for anonymous inquiries (look at how all the airline web sites are now starting to require identifying country of origin prior to giving quotes). The use of 2 might be a technology issue, a limitation of the system. But it does create an arbitrage opportunity, by doing a re-issue at a high-cost location (e.g. UK or US). But the preparations for 100% e-ticketing are also causing these systems to be updated, so the airline differences might be ending this year.