Were you thinking of the Mont Blanc tunnel? They are charging over E22 for bikes to pass. It was a 90 min wait to get through on Sunday. They enforce a 70kph limit and 150m spacing. It really isn't worth going out of your way. I will take the St Bernard pass (road) next time. The Aosta valley is worth a day or two of time however. To the North of the town of Aosta is an alpine road leading up through Ollomont to Glacier. Already pretty high, the road ends but there is a good walking track on up into the clouds. Glacier has a field for camping out, if you happen to have a tent.