As per the title. I have a few friends interested in this game but unlike me they have console and I a top end PC, will we be able to co-op and or play multiplayer together ? And if no then why?

Console devs have their own console specific form of multiplayer. Xbox has Xbox live, Playstation has PSN, and not sure about PC. They don't all tie in together.

Im vexed... the devs have let a round off in there foot before the game even gets going.

Doubtful the only game I know of thats does is portal 2 and if I remember correctly that only between the pc and ps3 Sony has really opened up psn to developers lately while xbl remains a very closed system, I don't really understand why you'd expect a feature almost no games have.