Good question, I don't remember. I think it wasn't filtered? The only thing I remember for sure is that when I was recently in the Netherlands, the 3IE content blockers weren't in effect. So I think it's the same when visiting the UK, falling open by default.
(Yes, I don't want to send my passport photo to 3IE, that's why I'm dealing with these blockers. And I heard that even if you do verify yourself, they still mess with the DNS records.)
Normally not, as historically traffic from roaming users has been "home routed". That is, it was sent over a tunnel (think IPsec or similar) back to the user's home network, where it left through their usual infrastructure.
Especially in late 4G and 5G, with ideas of low latency services (that would break if you did this), there are options to route traffic into the visiting network instead. Not sure if anyone's using this though.
I’ve seen this on IP lookups I’ve done when roaming - surely this is a bad idea for latency? What’s the motivation? Why would they cripple performance further by proxying to an endpoint that could be half away around the world.
This is especially infuriating as a European visiting the US, where a bunch of services are geo-fenced to American IPs. In several towns, I couldn't pay for parking or buy a bus ticket because the online service is geo-fenced and there's no brick-and-mortar alternative anymore. They also restrict apps in the play store or whatever to US accounts. I had to buy a cheap SIM card to get around all that. It's insane.
It's absolutely horrible - I was in California a few months ago and all my traffic was being sent back to the UK - 300ms ping and about 1mbps each way.
I recall now it was a Twilio Global SIM - I was just using it as an early global sim rather than building on it - all traffic went back to T-Mobile in the US it seemed
(Yes, I don't want to send my passport photo to 3IE, that's why I'm dealing with these blockers. And I heard that even if you do verify yourself, they still mess with the DNS records.)