Hmmm...
I'm not speaking strictly in terms of a single photon, nor of the squashing perspective, but of the effect of time dilation specifically and speculating about what it really is/ what causes it.
A single photon may not accelerate/decelerate. But consider the fact that in real life...
I was reading some interesting articles at wikipedia on black holes and time dialation:
http://en.wikipedia.org/wiki/Black_hole
http://en.wikipedia.org/wiki/Time_dilation
I remember this subject interested me greatly when I was in high school physics. I'm pretty rusty now, so bear with...