The problem I have isn't with the inference that the photons came from GRB 090510, but with the idea that anything can be inferred about the medium they passed through.
If quantum-foam fluctuations can be assumed to be uniformly distributed along the paths of all three photons, then the number of disturbances encountered by a photon is proportional only to the photon's path length. Here, the path lengths of all three photons are enormous and essentially identical, so it seems reasonable to assume that each one encounters a similar number of quantum "potholes," and that no difference in their arrival energies/times/whatever would be noticeable on a millisecond scale.
They would drift apart from each other, in a manner somewhat similar to the brownian motion. Essentially, small-scale foam would be similar to a slight inherent "blur" of the vacuum for gamma rays.
The problem I have isn't with the inference that the photons came from GRB 090510, but with the idea that anything can be inferred about the medium they passed through.
If quantum-foam fluctuations can be assumed to be uniformly distributed along the paths of all three photons, then the number of disturbances encountered by a photon is proportional only to the photon's path length. Here, the path lengths of all three photons are enormous and essentially identical, so it seems reasonable to assume that each one encounters a similar number of quantum "potholes," and that no difference in their arrival energies/times/whatever would be noticeable on a millisecond scale.