I’ve been in touch with a company called WSP who are working on behalf of Network Rail who in turn are considering building bridges to replace the level crossings in Everton and Tempsford.
It’s beginning to look very likely the bridges will go ahead. WSP have undertaken feasibility studies for their construction are now working on the funding. Provisionally, they are expecting the bridges to be in place in 2019/20.
Here are the maps: