That wasnt on board the hyperion, and also that was when raynor was surrounded with dominion transmissions. It would be easy for mengsk to enable a constant form of communication once he realized raynor was with valerian.
Compare this with the odin missions where horner was extra careful with the pilot and inspected tychus's suit. Had the transmission been open, he would have known.
Tychus doesnt have that much time after exiting the hyperion to warn arcturus of anything (if he wants to that is). Once deployed, the mission starts shortly after. Arcturus would prepare faster if he just listened to his local defenses.
You are correct. Recently I read the entry about Tychus on one of the SC wikis and it pointed me to the transcript of a Q&A session in which this very question was posed to the game developers. They said that Tychus's suit only sent out extremely brief and infrequent signals to Mengsk - basically letting Mengsk know that he's still alive and nothing else - and that a full connection wasn't activated until the very end when Tychus entered the hive.
I suppose if Mengsk secretly planned the entire invasion then it's not that hard to believe that he would trust Tychus to walk around without supervision - if Tychus didn't show up at the final battle, Mengsk would know.
Option A is bull!@#$ because it assumes that Mengsk is omniscient, somehow knowing that a rag tag band of rebels would start working with Tychus, who would start working with Valerian, who would get close enough to the Queen of Blades, who would use the artifact successfully and a host of other unrealistic assumptions..
But all of those assumptions become very realistic if one thing is true: Mengsk knew that the artifact would work and he felt that it couldn't be done without Raynor's help, so he tricked Raynor into de-infesting Kerrigan for him.
To me, that makes the most sense - why would he plant Tychus with orders to kill Kerrigan unless he was confident that Tychus would get a chance to kill Kerrigan? The only way he could be that confident is if he engineered the whole invasion himself.
That is, unless Tychus didn't have orders to kill Kerrigan and those orders only came at the end. But to me it sounds like Tychus always had those orders.
And like I said again, I find it really hard to believe that Valerian could borrow half the fleet without his father noticing. It is far more likely that his father let him borrow the fleet or flat out encouraged him to do it.
Oh and I'm just going to say that if there is anything in HotS that answers these questions please no one bring it up and spoil it for us. This is the WoL forum.