I suspect that there were contingency plans for Nightingale hospitals, supplies of beds, equipment etc. Buildings earmarked etc.
So when the call came the plans were dusted off and put into action.
I doubt if there are such plans for schools. ( there is an argument that it would have been possible to produce such plans when schools were shut down in March.)
To set up such schools will need money, staff resources, transport.
Not all staff will be available/want to come in. My daughter has been working flat out either at home, in school with essential workers’s children or from last week teaching as normal. Not sure if she and her colleagues would be happy to work right through.
I’m a retired teacher - but would need to have my DBS updating as would 1000s of others. This would take ages - it can take ages at the best of times.
Local Authorities do not have the staff to organise in the way they used to thanks to austerity.
So it looks like children will be given vouchers - great - but there will the 1000s of tutors be found. But Boris can then say that he’s solved the problems and the teachers/LAs/unions stood in the way of what he wanted to do.