When roaming, is your phone automatically provisioned for MMS?

Here’s a kicker of a question from Alfie about MMS provisioning whilst roaming.

I’m wondering when a person travels over an international border with roaming enabled, and they switch over to the partner operator, whether they then have the correct settings to send mms….

I’d say no, but a couple of people I’ve spoken to have said that they have been able to

I can’t quite remember. I’ve always just been able to send MMS using the existing network settings (or at least, what I thought were the existing ones) without having to change anything on my handset. Same with data. I wonder, I wonder. Does anyone have any perspective on this?