AMR has always agressively responded to startups flying "thier routes". Even though the RDU hub is much reduced from its hayday, AMR still thinks of it as "thiers". I'm only suprised that they didn't put MD-80s on these routes, with hourly service, for $50 round trip.
I'd guess the lack of response to XJT is because they aren't messing around in anyone else's back yard.