Mountain Bluebird in the Sandhills?!?

I woke up early this morning to investigate a possible Mountain Bluebird in a Fayetteville gated community with two of Durham's most famous birders, Jeff Pippen and Will Cook.  The photos we had seen looked really promising, but since this would represent just the second record for the state and the first for the Piedmont/Sandhills province(s), care has to be taken with assigning a label.

Wayne Irvin, who kindly arranged access for us (thanks Wayne!), had arrived before us and found the bird, but in typical chase fashion by the time we arrived it had eluded him.  Dang!

But as we exchanged pleasantries I pointed out that a bluebird was calling and it was re-spotted...

Well that's certainly a bird

...unfortunately at the top of the tallest tree in the area (hence the mediocre photos).

In bad light the bird looked dingy in gray with buffy/brown hints in the chest and throat, but once it eventually left its tree top and perched in some low pine saplings I could clearly see light blue in the wings and tail.

My best closest photo and she had to be looking away

It seemed to have picked up a pretty male Eastern Bluebird boyfriend and Wayne said that before we arrived they had been investigating a nest hole.  The pair stayed together the entire ~40 minutes we observed them and at one point the male chased the female who evaded him acrobatically.

star-crossed lovers?

I last saw them fly off into the sunrise together over the treetops toward the East-southeast just before 9 am. Looking at satellite images, there appears to be a powerline cut in that direction.  All sightings so far have been in the morning; maybe that's where they spend their afternoons?

My last half decent photo before she took her beau and bounced

Based on what I've read I don't think there's any chance that this bird is simply some sort of mal-feathered Eastern Bluebird.  Even if it were an Eastern somehow missing all its orange pigmentation it should still have a white belly and a bicolored bill, which were lacking on this suspect.

But the budding romance we witnessed does bring up the possibility of hybridization. I have read that Mountains are known to hybridize with Western Bluebirds and Jeff told me that there is a population of Eastern/Mountain hybrids, but what are these birds supposed to look like?  I can't find any photos anywhere.

My main hesitancy to call this bird definitively a Mountain Bluebird (apart from my lack of prior experience with the species and its rarity) is that I could not discern any shape differences in the field between the pair. The field guides I have in front of me, Sibley and Nat Geo. 6th ed. (thanks for the bday present, mom) say that Mountain Bluebird should have a longer tail, longer wings and primary projection. Even when the two were sitting branches apart or in flight together any differences were too subtle for my eye.

I did happen to capture a relatively deep fork in the tail of female, which I didn't notice until I reviewed my photos.

Could this obviously forked tail be an indicator for Mountain?

Both field guides show Mountain as having a more obviously forked tail and doing a Google image search I found that a few shots capture this in Mountains, but I could not find any photos of an Eastern with this much of a fork.

While I'm at it here are a couple more marginal shots of the bird preening that show some wing shape and primary projection.

Preening

She's got a date tonight; gotta look pretty

hmm does that count as "long primary projection?"