Yes they are. Gene Hunt got himself killed as a rookie PC and it's his body that's buried in a field underneath a scarecrow. He's been collecting the ghosts of dead (or half dead) police officers ever since.
When he said that he helped Sam Tyler to escape, he meant that Sam wanted to move on - to the pub, which represents the after-life for dead coppers. The creepy one whose name I've forgotten also collects the dead but he takes them somewhere else. He tells them they're going to the best police station in the world but you know what they say: If something sounds too good to be true, it probably is. He claims all the crooked ones.
Sam never did come out of his coma. He realized that he was still asleep in the last episode of Life on Mars when he squeezed something sharp in his hand but felt nothing. He jumped off the roof to get himself back to the action.
Drake died in hospital at 2:06 (I think) and she chose the pub, as did the other three. Gene had to stay behind to carry on his work. He hopped back in time, as only ghosts can do, ready for Sam to arrive.
All clear now?
