If Airbnb is importing both myallocator's calendar and one from another site, will they override each other?
Having two different calendar's exporting availability info into Airbnb will cause conflicts.
This is because each time Airbnb pulls data from either calendar, it would update its availability with the latest information in that calendar. This is similar to how having two PMSs connected to myallocator conflicts.
When setting up Airbnb, make sure that myallocator is the only calendar that Airbnb is importing availability information into.