If we speak about services that exist in the same ThingWorx instance, the answer is no. Those services do not communicate via REST, but internally in the ThingWorx instance (directly in Java).
If we speak about services between different instances, I do not have experience to say it's impossible (just a gut feeling that the answer is no). Those services would anyway be executed through Federation, not as REST services, so also this things points me to say no.
