Slightly off-topic "tenders"

[YSV-205]

Slightly off-topic "tenders"
Can someone please explain how tenders are won & lost by various bus companies. For example, what's involved, what goes into them, costs, what needs to be proven, are there reasons why a route could be in a position where no company is willing to tender for the route; what happens then, reasons why one loses a tender & another one gains one, how often are tenders up for renewal, etc. I would appreciate an example if someone can use figures (£ figures) so I have a better understanding