Q: Can a formation enter play via a Webway Portal that is covered by, or is in the zone of control of, enemy units?
A: Yes, but the formation using it to enter play would have to carry out an engage action.

Q: What happens when a formation in reserve fails its action test and needs to enter play via a Webway Portal that is covered by, or is in the zone of control of, enemy units?
A: It takes a Blast marker, and may not take a hold action. It effectively looses its activation.

Any units that are out of formation for any reason after a formation has taken the movement part of its action are destroyed. The controlling player may choose which units are out of formation and destroyed. Note that each unit lost will place one Blast marker on the main part of the formation. This applies after each individual move, so if a formation made a march action, you can’t wait until the end of all three moves in order to bring units back into formation—any out of formation units are destroyed at the end of the first move (and again at the end of the second and third moves if any other units have also ended up out of formation following the move).

Thanks greg, you kinda want you gate as the tnh objectives for reach which the opponent sets up. A warlord could be on it at the start of turn 2 and block you coming through. Doubt youd kick him off. Im guess it just forces you to be safe and make it your blitz.

Just to note, i gather in Epic UK at least webway portals will be able to be blocked going forward. So if a stand completely covers it nothing's getting out and must be knocked off before a unit inside can get out.