Peter Masson wrote:

Aylesbury to Claydon has booked trains (binliners), and because of the low
speed and long block section the binliners wouldn't actually leave a lot
of time for testing.

During the morning the section from Claydon to Calvert is used by arriving
and departing Avon binliner. The Cricklewood binliner then arrives in
section at 13:40, running down to Calvert where it is then locked in the
loop, where it remains until early evening. The Dagenham Dock binliner
follows it down from Aylesbury at 16:40. Things then start getting very
busy: the Cricklewood empties then return, followed by the Ripple Lane
empties, then the Northolt West Waste binliner runs down and returns almost
immediately. By that time it is approaching 01:00!

In addition to those there are the rarely used test train paths for class
16x testing, the 5T00 09:40 and 10:20 Aylesbury to Claydon and 5T01 11:20
and 12:05 Claydon to Aylesbury paths.

So, quite apart from the infrastructure impracticalities, it would be a
complete non-starter.