Can the Xbee-PRO XSC S3B be programmed with the Arduino IDE? Where do I find the definition files?

No it can’t. The XSC is ONLY for existing customers who are working with the old 9XStream products. It is not something that should be used with NEW applications.

It also re-assigns some of the PIN’s to make it compatible with the old XStream which in turn makes it not compatible with most 3rd party boards.