I just wonder if this is a recent spot. There are no contemperary cars surrounding the GTO. I wonder because on the Dutch frontpage of autogespot there is a short item about this car, that it was spotted for the first and last time in august 2011. I think that is about the same time that you spotted it in Bremen.
You are absolutely right, these photos are quite old (2011)
It was actually the first time I've seen this one. I have seen it a few more times over the years, but was never able to get better shots of it. I do have more pictures, but I made them with my phone. The last time I've seen it was in 2018. It shows up very unregularely but I'm quite sure this one is still registered in Bremen.