I was flying today SIN-SYD in QF on the A380 (first time for me in this aircraft) in F. Part of Aadvantage Award itinerary.
when arrived to SIN, an agent was waiting with a sign with my name and told me the flight was delayed from LHR more than 10 hours, and I was moved to Singapore Airlines.
I was hesitant at the beginning with the switch as I wanted to fly on the A380, and the only option was to wait 10 hours as other flights to Australia were all completely full.
but I ended up accepting the change, maybe the one in a lifetime chance to get to know SQ service in First. Which indeed was very nice.
I was impressed how Qantas took care of the situation, very prompt and professional, a guy drove me to the Lounge to do the paperwork. Considering I was flying on an award ticket I was not expecting any switches on carriers for a 10 hour delay.
Couldn't you ask for CX instead, as they are better than SQ IMO?