The infantry are based on 60x40mm. I was going to put them on 40x40mm like my light infantry but I couldn't find any and couldn't be bothered cutting them out of 3mm balsa wood so went with what I had in my supplies box (I was away from home when I painted these you see). I generally use the 40x60 bases for my infantry to try to keep bayonets inside the area of the base - something I decided to when I first started painting plastic infantry. The artillery base is about 110mm diameter - give or take.
I have not really based these for any particular rule system. Using similarly based models I have used my Napoleonics for Black Powder, General de Brigade, Piquet and a few others.
Cheers
Brian