When I was at T4 last week I looked around and it appears that once you enter T4, they do not have regular exits like they do at US airports.

When you deplane, you enter a lower hallway that goes to immigration and to connections. When you are transferring to another flight the hallway splits from the immigration area to a connections area where you go through security and are allowed back in the post-security area.

While I was walking around that post-security area, I did not see exits.
I do not believe you can simply exit T4 once you are in the post-security area without going to the lower level and thus immigration and customs.

So they must have some sort of contingency plan in place for emergencies.