The thing with Hybrids is that they really aren’t like a Volvo B9 or even Scania DC9 equipped vehicles with an Ecolife.
The B5LH hybrids if they are cruising at 50mph causes the engine to strain in the same fashion that Voith fitted diesel units do at high speed.
Not great for keeping the noise down.
Volvo B5LH chassis, because they're self-charging hybrids, their whole driveline is best suited to 30mph. light acceleration with progressive light braking in advanced of stopping to help maintain there battery power, as they're parallel hybrids their electric motors are small in comparison to a full electric bus motor. The pause between gearing can also be a grating factor when so used to Auto-Diesels.
Hybrid buses are often heavier than their diesel-only counterparts which also blunts their performance from a standstill.
The number one reason why I hated driving the 7900s at Lothian.
Some of the B9TLs that Lothian used to have were extremely fast at speeding up (not extreme but felt quick). I have a memory of a B5 and a B9 at a junction, the light went green and they both went ahead. The B9 got ahead quickly although I have been on some sluggish B9s as well.
(Yes I am aware that buses aren't racing cars and that I sound a bit like some certain groups of people; these are all from past experiences and I am not saying "oh all new buses are bad, bring back euro 2 bus")
It’s a similar circumstance to Glasgows B9TLs, the control with which engineering management are maintaining the correct software control. Engines and gearboxes haven’t been configured the same way on all vehicles, possibly some were missed if it was previously changed.