Dutch families have on average 1.3 cars for a family size of 2.1. The families with a car use about 947l/year of fuel. That is 79l per month. So with that 1.2¢ fuel price lowering that would save every family 1€ per month.
Meanwhile the same money can save 127-49=78€ per person using Dal Vrij currently. Even if only one person in a family is using the subscription (which I doubt will happen, its too good of a deal) you're already ~75x more effective than the fuel lowering
This ~75x number seems awfully similar in a calculation I made last year which compared the tax payer's price of commuter traffic per 1000 km traveled per capita. Trains where 70x cheaper or so iirc. The difference is ofc that the 70x is paid by road tax mostly but its still and awful lot of money.