Thanks for keeping it up to date.

https://www.milton-keynes.gov.uk/news/2023/part-a509-be-closed-monday-25-september-2023 says the job should be finished now, but live bus data https://bustimes.org/services/x5-bedford-milton-keynes#map says otherwise, but the bus Co.s uploading their routes to the public source bt.o use may not have updated it yet.

Do you know if it's finished yet?

OSM has the X5 route going along London Road, not the alternative route via Willen Road. I might reinstate it along London Road if it's due to finish up and go back to the way it was.