Hello Craig,
Basically, it is possible to sync Hotel Booking and Booking.com calendars using directions from this article.
However, as far as I know Booking.com does allow synchronization of properties with a single item assigned to it only, which means if you have more than one item under some property, the option to import/export will not be available for such property. I would recommend that you also contact Booking.com team to get more information regarding this matter.
Regards,
Andre