First Glonass is a mess, missing quite a few operational satellites Galileo is just ramping up.

Interms of what is broadcast they still work on the same principle satellites broadcast time receiver does something like a linear least squares fit to estimate position, and time.

Mixing all the sources and doing a linear least squares like fit means the bad guy has to spoof more signals, and this system will be more robust but it is susceptible to the same attack just ramped up a bit