Well, (as far as I understood) up to Shadowrun 3rd Edition, combat initiative was rolled (reaction + initiative dices) on the following way: (please correct me if i'm wrong)
Merc 01 > Rolled 32
Merc 02 > Rolled 27
Thug 01 > Rolled 13
Thug 02 > Rolled 09
1ST "ROUND":
Merc 01, Merc 02, Thug 01, Thug 02
2ND "ROUND":
Merc 01, Merc 02, Thug 01
3RD "ROUND":
Merc 01, Merc 02
4TH "ROUND":
Merc 01
Now along with Shadowrun 4th Edition we have Initiative Passes... can someone explain to me how does it work? I've searched for it here, but i was unable to find an answer...