Yes. I've done so with an AA-issued e-ticket without it being reissued. In my case, it was changing from CX to JL for HKG-NRT. When I called the AA RTW desk to make the change, they did it in like 10 seconds, and for no fee, and without having to send it to the rate desk for analysis. This last point was a pretty good indication that no reissue had occurred.

There was a minor disruption at the airport, as the new reservation didn't have the old ticket number on it. Once that was straightened out, all was fine - JL was able to lift the coupon that was issued for the CX flight without a problem, even though it had not been endorsed or reissued, and even though it was an e-ticket. Lesson: always have e-ticket numbers handy.

One issue I can see is that if the ticket is not re-issued or endorsed, you rely on the airport personnel knowing that they can lift the other carrier's coupon for that segment without endorsement, since it's allowed in the fare rules. I suppose there's always a chance that you get someone that doesn't know the rules and doesn't want to get in trouble, but this can probably be solved at the airport by escalating the matter to someone that does know, so it would not bother me to travel with an un-reissued xONEx ticket that had a change of carrier.