Intresting article ! : http://www.sciencemag.org/news/2017/01/can-escaped-pets-rescue-endangered-species
I don't really see this as anything new - whilst I can appreciate that there's likely a stigma attached to pet trade and escaped pets from the established zoo/conservation breeding programs; the fact that there are populations which can be made use of outside of those systems is nothing new. Using such populations to be a donor source would, I think, already be in use. Of course quarantines would have to be used; a lack of breeding history might be a problem for breeding programs, but would at least present a new avenue of stock (although one would expect there to be limits and potential risk of in-breeding - but then again if populations of a species are that low to require such action as this chances are in-breeding to some degree, is going to happen). You'd still need to have reintroduction programs and such animals might only be directly in use for breeding up new generations who could then be trained and put into reintroduction programs.
Purity of such populations is a problem. Among the examples mentioned, escaped parrots are in most cases several races released together, and 'bantengs' in Australia are domesticated Bali cattle - the same one which exists in millions in Asia, quite to the opposite to the wild banteng.
