There is still no official statement about the dates of the July work
Yes, there is. It's been uploaded on the site of the Trenitalia's sister company that owns the tracks and that is responsible for such works: https://www.rfi.it/it/rete/i-nostri-progetti/I-nostri-progetti-regione-per-regione/toscana.html
Passengers going to Florence should pick Firenze Campo di Marte from the "TO" field on trenitalia.com . Those going north, beyond Florence, will have to take a substitute bus to transfer between Campo di Marte and SMN.
And rather than waiting to find out whether there is a strike or not.
There is no strike, and since Campo di Marte is quite central there is no need to take a slow bus. Please, do not mud the waters with confusing speculations.