We have a MONDEO PARAMEDIC car at work at the moment.In for repair.Yes they do bolt to the roof .When they are sold on,they just put gromitts in the holes.Then the person that buys it (usually a dealer ) welds up the holes and paints the roof and also repairs the dashboard as they have a lot of equipment scrwed to them.

Also the electrics are put back to standard before they are sold.The MONDEO at work has 16 switches on the dash that make the blue lights flash,sirens,blue light in front grille and headlights flash e.c.t.