There is one taxi service in the area, but it doesn't work like a taxi stand, you need to call them and book ahead of time.
I would suggest getting in touch, asking for price estimates and, if you want to go ahead, booking a date and time so that you know you will have the transport. Don't wait until the last minute. They are called Chianti Taxi - http://www.chiantitaxi.com/
my wife and I stayed in Tuscany in January, a really fantastic place !!
Absolutely to visit Lucca and Pisa. We also did the wine tour, and we hired a taxi with driver ( Chianti Winetasting Tour )
If you need more information, ask us. We also ate in excellent restaurants