You'll need to see the breakdown by region. For example, a lot of people commute in/around Belgium or Switzerland, but not a lot of people commute to/from Polan

You'll need to see the breakdown by region. For example, a lot of people commute in/around Belgium or Switzerland, but not a lot of people commute to/from Poland. The rail links in certain parts of "old" Europe are already very good (or sufficient). But the OP mentioned cross-continent (I assume he means cross-EU).