Most casinos accept the transfer of VIP level since they understand how necessary it is to accept and beneficial it is to their business to accept high rollers; the question at this point should be which casinos don't accept VIP level transfer?
I just heard this VIP transfer as im not into gambling really, i just do bets, win or loss, nothing else about the VIP programs. But it sounds like great idea for what you point out. I just thought it's more like as a competitor, "why would i let my user go to X casino and benefit them too for what this user do towards us". For the receiving casino it will be great pleasure to them. But what would be the benefits to the one sending casino?
The possibility that a VIP gambler can transfer out to any casino and take their VIP status there will keep every casino on their toes to make sure that they do not lose their high roller to another casino. To make that happen, they have to make sure to keep VIP rewards attractive. If they don't, another casino with a more attractive reward or offer may just begin to look attractive to them.