Will this game have campaigns?

[Mono.]

If so, will it be one big, divided by chapters storyline, or will it be like in Left 4 Dead, with shorter, standalone campaigns?

Or, will it have no predetermined campaigns, and all maps will be randomly generated? ("Tile-based map generation tool").

[Taikis]

TileGen is primarily a tool for level designers. You can build sets of rooms and corridors, then easily rearrange those pieces to make a final level. You can also specify some generation rules and the tool will randomly generate a level for you out of those pieces.

You can build and play the level right from within TileGen, but you generally want to take the output into Hammer for refinement and building into a full campaign.

Best info at the moment.