Ann: Trading Halt, page-76

I don't necessarily think they would have to halt regardless of size.

I personally think (maybe hope) that it's a contract big enough to get some press... The other player (eg. U.S. Military) may well be looking to announce the contract in some official documents or ceremony... Might have arranged a press conference or something. This will take time( a day or so) to organise.

I would imagine alexium are probably gagged from talking about this 'win' until the other party announces the deal. This potentially creates an insider trading situation unless they halt until the counter party officially announces the deal... Hence trading halt.

Just a theory really.