I got it from 10 years of design and analysis experience with the underlying protocols; that it is impossible to "spoof" calling party ID in properly configured SS7 networks whose operators do not configure trunks to _customers_ as if they were trunks to _network equipment_ is simply a matter of fact.
As all the interworking standards make clear, any interworking to a protocol which does not differentiate between customer-provided and network-provided calling party identification must either use the supplied number as a customer provided number only, or replace it with the BTN for the trunk.
Thor Lancelot Simon snipped-for-privacy@rek.tjls.com
"We cannot usually in social life pursue a single value or a single moral aim, untroubled by the need to compromise with others." - H.L.A. Hart