Boeing have done similar before with the SQ deal, they made sure the A310s and A343s were taken out with the deal.
In that transaction Boeing purchased already-delivered planes. And they did not require SQ to cancel their A340-500 order nor compel them to buy the 777-100 instead (which SQ had been looking at for ULR operations).
I'm sure there are past deals where Airbus or Boeing agreed to help cover the cancellation costs if a customer switched OEMs with undelivered orders on the books, but I don't believe either OEM can legally compel (via contract) an airline to cancel orders with the other OEM in order to place an order with them. The EU demanded Boeing rescind their exclusivity contracts with AA, DL and UA to approve the merger with McD so I am sure they would take action on Airbus' behalf if Boeing tried such a tactic and the current protectionist bent of the US government would almost certainly back a Boeing complaint if Airbus tried it.
When corporation do contracts with each other a lot of possibilities exist. Hawaiian making a contract with Boeing, buying the 787 and Boeing paying the cancellation cost at Airbus for the A330-800 is completely in the realm of possibilities, nothing forced about it.
Why should Boeing do it, with the 787 selling well to willing airlines? My only explanation is that Boeing is afraid that once the A330-800 is operating at one airline, others would follow. UA at least seems to consider buying the A330-800, perhaps other airlines are considering it too and Airbus had good reasons to build the A330-800 and certify it.
The SQ Boeing A340 deal shows to what length Boeing is prepared to go to keep competing frames from desirable customers.
This Hawaiian deal seems to have gone wrong. IMO Boeing did the whispering, had the rendering ready and something went wrong.