Most trains in the UK, and to my knowledge all high speed trains, are electrified, and your link states that electrified services are not subject to this duty.
Not even all the main lines in the UK are electrified, and there's still a large stock of 1970s diesel "High Speed Trains" (yes, that's the actual model name) in operation on main lines.
The main lines:
- Cross Country Route: partially electrified;
- East Coast Main Line: fully electrified (but a number of services continue north of it, which is not electrified);
- Great Eastern Main Line: fully electrified;
- Great Western Main Line: partially electrified (for the first 11 of 120 miles);
- High Speed 1: fully electrified;
- Midland Main Line: partially electrified (again, only for a relatively short distance near the London end);
- West Coast Main Line: fully electrified.
That's 3 out of 7 main lines that are only partially electrified. If we get off the main lines (and quite a number of smaller lines still have frequent services, all diesel!).
