I couldn't find a definite statement on this.

Sometimes I had the impression that after I jammed a gate with no units on it, units still appeared from that gate.

So I wonder, if I jam a gate or lockdown an OP, can units get through or leave that tick? Maybe if a player orders his squads to leave an OP before I initiate the Lockdown on the same tick, do they get away?
Oh, and if I lockdown an OP, are units that arrive there after the lockdown started trapped there?

A clarification would be appeciated.

Jamming a gate only stops it's ability for allowing troops to teleport there from other gates and your base. Any other troops can move there and leave there at will.

Locking down any op means that troops that don't leave before the lockdown are stuck there and any other troops that land afterwards are also trapped until it wears off, that includes your own troops as well.

When you jam a gate, that prevents the owner or the owner's allies to jump to the gate. If there are squads in the vicinity, they can still move to the gate but they cannot jump there. To lock someone down, you need a spy and enough inflitration ticks. When a place is on lock down, units cannot go in or get out of the area.

Hope this helps

what about when you build a portal? I just built my first and it is already obstructed automaticly, is this a bug? if not, why does it do this?

Gates are jammed when built for game balancing. You can use it after 3-6 ticks.

What happens if you jam a colony under protection or activate a shield to a colony that's locked down? Does the ring/dome turn purple?

If you liockdown a colony u need to jam it also to prevet troops from gating n. Jammin revents gating and radar lockdown prevents entering or leaving by flying