I don't think so, carriers are quite clear about their conditions. E.g. even if you're not French you can understand on this webpage that you have 40GB/month, included in Europe, for 24,99€/month: https://shop.sosh.fr/mobile/forfaits-mobiles
It goes to show why carriers lobbied so hard to prevent European citizens to buy subscriptions from a different country considering roaming would truly create European competition between carriers.
Keeping in mind Dutch,French and Belgian carriers are sometimes one and the same entity it shows liberalism and free market is only promoted and applied when it benefits the strong (carriers), not the weak (consumers).
It's still a very good and welcomed evolution for consumers though :).
Cross country competetion would really suck because of the varying levels of wellfare across the EU.
Between Belgium France and the Netherlands, there isn't much of a problem. However, if you start comparing e.g. the Netherlands with Romania, things get weird. Those consumer markets are vastly different, Romania is much cheaper.
I'd expect that, due to differing expectations of infrastructure building a network in Romanio would also be cheaper.
