TCX are a charter airline and so do not sell the seats or overbook, this is done by the tour operator, in this instance Canadian Affair. If you are talking about the TCX5K this was meant to be operated by a 757-200 with 187 seats, and if an aircraft change was done it would have been to a 757-200 with 235 seats, which have subbed in a number of times for the 187 seaters and so would have more than enough seats to carry everybody. If the aircraft had of been downgraded then of course TCX would have required volunteers for offload but that is not the case, Canadian Affair needed to offload as they had oversold. I have know C/A overbook the 187 seaters by 9 before so maybe 30 on a larger aircraft isn't so unbelievable! And as I said before, C/A would provide the compensation/welfare and rebooking, not TCX.
Mark