Lycamobile's new data roaming packs
 

Actually, Lycamobile doesn't have a good reputation here. The last "free roaming" offer was just a fake. They redefined roaming as "calling home".

But now Lycamobile has launched data roaming packages for about 16 mostly EU countries:
http://www.lycamobile.de/en/bundle?id=6

In short: It's the best offer for around 1 GB per month in EU roaming for 12-15 € which is on the German prepaid market.
Unfortunately, it's only 14 countries so far and France and Portugal are priced higher.
But for the given countries it's on par with the German domestic data rate.

So, for the 1st time, there is an alternative to buy a local SIM Card for this data volume. Even Lyca's offer is a bit higher than the local prices, you don't need to pay start up prices for the starter packs and can configure your SIM already at home. Lyca's SIM cards are sold in Germany for 9.90 € with 20 € credit on it.

Some restrictions should be mentioned: no tethering allowed - actually it's blocked, no upsize add-ons available, packs strictly for 30 days, SIM will be deactivated after 180 days of non-usage which is quite fast for a German Card.

I still don't know if they hook on Vodafone's roaming Networks (which is their MNO in Germany), but I assume they break out and use their respective local partners for roaming instead.

I would assume that they upload a local Lyca IMSI to the SIM once they see the SIM in a Lyca country. They already had some similar offers in the past for two countries combinations (e.g. UK-Ireland). Like Togglemobile but without assigning a local phone number and with automatic IMSI upload.

That would be in line with only offering it in Lyca countries and with the fact that they instruct to wait for a text indicating that the roaming is ready.

Even so, they seem to give out an UK IP address in all Lyca countries.