OK, I downloaded a police vehicle with sirens and light bar. The animation works for a single vehicle if I use
this animate ["ani_siren", 1];
However, if I select the teamleader and write:
{_x animate ["ani_siren", 1]} foreach units group this
It doesn't work, I don't get an error message though, so I think it's caused because the unit itself refers to the driver not the vehicle. I suppose the is other word for it to work. Thanks for the help.