I have had varying luck with this as well. A group of us ate at LeCellier once. Only one person had a TiW card, but there were a few that wanted to pay with their own room cards. The server told us that all the food had to be on one check, with one payment...so no splitting.
Last Dec, a group of about 7 of us ate together frequently. There were 3 TiW cards at each meal. We let the server know, when we ordered, that different 'groups' would be paying with a specific TiW card discount. No problem.
But, we have never been able to have one person have a TiW card, but have others get the discount but pay with something other than cash on that one bill. Our servers always told us that if a TiW card was used, the payment (if credit or room key) had to be in the TiW card holders name. Everyone could put in cash, and then the TiW holder could use a credit card in his name, to pay the entire thing, or he could use his cc (or room key) to pay his share with cash from others making up the rest. But the server wouldn't take multiple cc's for the same check...and still give the discount.