Vatican City State can't have more than few dozen vehicles, so it would cost at most a few million to be the first EU state to go completely fossil-fuel-free on their transport fleet.
Electrification of their railway station could be a cost, but it's so short you might be able to use a long enough train that the locomotive never enters the sovereign area.
Vatican is not even in the Eurozone. Just because it use euro it doesn't make it in eurozone, there are plenty of countries which are using euro without being eurozone members.
Electrification of their railway station could be a cost, but it's so short you might be able to use a long enough train that the locomotive never enters the sovereign area.