That's easier if there are a finite number of players (eg TfL and half a
dozen "Network Southeast area" National Rail companies). Scaling it to
numerous authorities operating independent bridges could be a problem.
Imagine a different operator was charging tolls for every road bridge
from Tower Bridge to Windsor.

Actually, E-ZPass has solved that remarkably well, with 22 different
authorities accepting each other's passes.

They did trials using it to pay at McDonalds' drive-through on Long Island,
but nothing came of it. Since you have to stop to pick up the order anyway,
tapping a credit card doesn't slow the process down much.

R's,
John