There is no scope clause.
The FWA would prohibit such a substitution, a transfer of business..For the same reason, Jetconnect will not be flying domestic sectors as if the union woke up it would be challenged. However am told the union folded quickly with an idle threat from the little fella that the 787 would go elsewhere if the agreed to, and FWA ratified, contract for the crew rest was not amended in Qantas' favour..The union didn't challenge, just folded.
However, the tried and trusted method of Oldmeadow (IR) is to send out messengers (think fleet managers, and wobbly pilots) to carry a message of a subsidiary flying the said aircraft, the pilots panic and fold...
Wash, rinse and repeat..
