There is an item on the BBC website here, clearly drawing on the recent Network Rail news release:
www.bbc.co.uk
£40m rail upgrades for Cambridge South station completed
The building of a new station in Cambridge reaches a milestone.
A £40m project to upgrade the railway infrastructure around a city's new station has been completed.
The South Rail Systems Alliance (SRSA) needed to upgrade sections of the West Anglia main line, as part of the building project for Cambridge South station.
SRSA won the contract for the works in September 2023, which included remodelling a branch junction at Shepreth.
Keith Sullivan, a programme manager for Network Rail, said it was a "major milestone" towards completing the station, which is expected to open early next year.
The main difficulty for using the busway for rail replacement is vehicle availability. Neither Stagecoach or Whippet have many spare guided vehicles. It is also important to remember that the southern end of the busway can't use double deckers because of low bridges.The busway might work to Cambridge main station, if they can persuade Stagecoach to provide a lot more services on the busway to cover planned engineering works, assuming they actually have enough of the specially-modified vehicles, but for very short notice disruption cover, it could be trickier.
I agree with this.I suspect that Cambridge South to Cambridge North rail replacements would also be better off going "direct", the long way around using the M11 and A14 to avoid having to fight their way through the centre of Cambridge, which could easily take twice as long, I'd guess. At least.