Does a 3-year PhD experience in a non-German EU university count in determining the salary for a TVL-13 (100%) position?

I worked for three different universities in the same Bundesland (state) in Germany. Although they all followed the same general regulations, the interpretation was rather different.

• one considered my PhD (on a scholarship, so not employed) as relevant experience, one not.
• one said my Cambridge University (UK) degree was a Fachhochschulabschluss, one considered it as full university degree.
• one was willing to negotiate (not with me, but with the institute that I should work for), one was not.

So you need to talk to your future boss and to the university that wants to employ you.

If the position is project funded, it may depend on the negotiation with the project leader. If it is a state funded position, then it should be up to the universities' policies. However given your experience, I think is unlikely that they only set you up for the first level/Stufe.

In the end that is something you can only clarify with your potential future employer. However, so far - from the little experience and insights I have - both options can occur: I know people who worked for the public administration before (which in the end is also paid according to the TV-L or TVöD) and started on Stufe (level) 1 - while others with just practical but related job experience started in a higher Stufe (level). So in the end it most likely depends on your institution and its flexibility - as well as your negotiation skills (and the availability of other applicants or the lack of such).