What Airprox?
Domitris uses a digital SLR, with a 400mm Image Stabilized lens. With the digital SLR sensor being two thirds the size of a regular film SLR pickup, the lens is magnified to the power of 1.5. This means that his camera has the use of a 600mm lens, and that's before he has possibly used his teleconverter. This is a huge magnification. And when sitting on top of a hill above the target aircraft, he gets some fantastic shots.
The Dominie crew is certainly flying within the limits.