Bus networks can work over small high density areas. Johannesburg has been building a bus network with exclusive lanes for years, but it’s designed to work in conjunction with its part complete metro. Cambridge, UK, has limited “busways” which connect the local villages. However, over large distances, I fail to see how buses can be more efficient. A single train can move hundreds of people over hundreds of kilometres, at much higher speeds than a bus, and with very little pollution.
I'd say it can work if there's no existing railway and/or there's not a lot of people traveling this way. Or maybe for short duration, like one or two months a year
Apart from Gibraltar I guess
But the definition of Europe will change depending on who you’re talking to and what your talking about.
A lot of the rail replacement currently is due to staff sickness ... Covid has hit a lot of things very badly.
Positively, the government has heavily supported rail through the pandemic. (estimated 22 billion pounds in 2020-21, up from 11 billion in 2019-20) (1)
Mostly to make up for loss of passenger ticket income.
Investment in High Speed 2 is also continuing despite the current situation, which I'm relatively hopeful about.
On the other hand the government has demanded cutbacks on operations to possibly 80% or less of pre-covid, and there seems to be a lot of overcrowding in some areas where the demand has rebounded faster. There is also a fairly widespread withdrawal of much of the onboard catering :-(
(1) https://assets.publishing.service.gov.uk/government/uploads/...