(13 Aug 2023, 8:31 am)Unber43 wrote Or have a plan on where to park buses before and park them in the correct location, or have them in the order for them to leave the depot

That's not always possible, and even if you do manage to get it right then it'll inevitably be thrown off by drivers finding defects with vehicles during first use inspections. 

There may also be reasons for engineering to want branded vehicles off route. For example if something is returning after major mechanical work, it's likely to be kept relatively local for at least a couple of days to bed it in - i.e if an X10 MMC has just had major work completed, I'd say it's extremely unlikely to be allocated to the X10 on its first day back in action.

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(13 Aug 2023, 9:01 am)Storx wrote  It's much better to do what Arriva do and have them as vehicle type and anything goes out on anything pretty much.

Believe Stagecoach is similar but they do it by vehicle type rather than Double / Single / Midi.

Arriva also do it by vehicle type, rather than Double / Single / Midi. 

For example all Blyth X10 and X11 boards are down for VDL DB300 Gemini's. 

In reality though, there's no real difference between an E400 and a DB300 to them, which is why they'll be used interchangeably. It's obviously different at Stagecoach where they only have 1 type of decker.