I was kind of hoping Les McLean would show up here... He has some beautiful examples in his book. He even shows the same negative (well - three different frames with the same exposure) developed in three different developers. No difference in the "spillover" from what I can see!

The factors contributing to this are:
1: Halation
2: Flare
3: Hydroquinone acceleration.

3 is related to infectious development in that both are caused by the reaction products of hydroquinone being more active than HQ itself, but that's as far as the similarity goes. Infectious development would lead to totally featureless, blacked-out highlights; which is not what's happening here (got a scan, Aggie?).
Since the spillover is seen with all developers, not only those containing hydroquinone, I assume this is a minor factor.

Halation and flare are more difficult to control by chemistry...