GPS works on 80x units but not pendolinos or class 220/1.
To clarify, GPS is one of four satellite positioning systems available. The latest receivers that can process all four simultaneously are called GNSS devices.
The latest Racelogic GNSS devices work very well in most trains including 390's especially when connected to a high-gain antenna as close the window as possible. However trains with a metallic UV reflective layer in the window glass reduce the signal strength available. Class 22x are the worst with very weak signals.
On the odd unit there appears to have been a 'blown' window pane that is blurry to look through but seems to allow better GPS/ GNSS signal.
I also discovered that the emergency window panes on some trains seem to be slightly different and allow a bit more GPS/ GNSS signal in.
Of course the vestibule glass is good for GPS signal on 22x, but not an ideal place to stand for several hours unless you sit on a tip down seat on a 222.
CAF class 196/197 / 397 window glass does seem to allow a bit more signal into the train than the glass on 22x, but the signal tends to be noisy and speed / position data is not as clean and calculated speeds can jump around by a few mph.