If it's obvious that you have no intention of going to TIA they will absolutely not let you board. Also, if it's obvious that you can't enter TIA they won't let you board.

The question is, what will they ask for, and will it be obvious to them?

A lesser concern is anything that CX may do after the fact (invoicing you for the money you owe them, banning you from future travel on their airline, reporting to the Chinese authorities that you may be attempting to illegally enter HKG). These all seem pretty unlikely but I would not totally discount them.