If halted all hell could break loose because we are not accustomed to such events. (Did we not have a halt about 2 years ago? Though with news not earth shaking.)
As for reason for halt, agree hostile take over is prime candidate. But there is also a possibility of another Eagle type discovery.
Could or would Noront hold back news? We went over that topic here before = Answer, Certainly. Noront would only need to prevent news leaks about info they hold. I happen to believe, and definitely suggest, that they are often doing just that.
Noront need not request a halt. TSX in their judgment could do so on their own provided that they have some information from the company that they deem appropriate or necessary to act on.