I (accidentally) got MR points for travelers cheques a couple months ago.
I called to order the cheques, and was asked for a checking acct #. I asked if I could give a savings acct #, because otherwise I'd have to wait a couple days to transfer the $ btwn accts. The rep said that a savings acct was fine.
The charges didn't show up for over a month. I looked online, and found out that you're only allowed to charge travelers cheques to a checking acct, not a savings acct. This was clearly the problem.
I needed to order more cheques anyway, so I called back. I ordered the new batch with my checking acct, to prevent any more problems (they were debited from the acct w/in a day or two). I told the representative that there was a problem with the payment with the last batch of cheques I ordered, and asked to resolve it then, because I was about to leave the country for several months. He said it showed as paid (!) so I let it be. I was hoping at this point that I would get the cheques for free -- I'd already received them, my acct hadn't been debited, and it showed as paid in AmEx's computers!
A few weeks later there was a charge on my plat card statement for "returned gift cheque item" in the amount of the travelers cheques. I paid it off and received MR points.
So, at the end of it, I had use of both the money and the cheques for about 6 weeks, and got MR points. This clearly isn't supposed to happen, and I don't think you should try to scam the system. But if you ask if you can pay with a savings acct, and they say it's OK, I'd go ahead.