In the US, there is no requirement that a carrier has to put you on another carrier because of delays. The most any airline will have to do is to book you on a later flight or to offer you a refund (even on non-refundable tickets. Hotel rooms, meal vouchers, travel on other carriers are done as a result of the carrier's customer service initiative.

If you are travelling on a discounted ticket and it is endorsed, I believe the carrier transporting you will charge the original carrier the lowest non-restricted one-way fare for the route. Thus, the fare charged is not necessarily a full Y fare. Also, from my experience in the US, at no point does the transporting carrier charge the passenger an additional fare collection if the passenger was travelling on a discounted ticket to begin with.

Merry, that is a very smart trick.

As for plating away, you can ticket travel on wholly with another carrier at www.united.com.