Our flight got in early and immigration and customs was no problem. We took the Malpensa Express train service operated by Trenord to Milano Centrale. The airport station had smooth wheelchair access to the train--elevators to the ticket office and platform and a no step plank to train. However at Milano Centrale as well as Porta Garibaldi, there are two large steps down.
The Sala Blu is an office at larger train stations that assists passengers with disabilities. For our Frecciarossa high speed train to Florence, they arranged for a wheelchair lift at Milan which worked well. And sorted out some confusion regarding getting a seat with wheelchair space. Hopefully it will go smoothly in Firenze as well.
The train has free wifi but due to Italian law, they require a credit card transaction. ..of 1 cent.