It's actually far more beneficial game theory-wise for miners to not signal with their hashing power till after the UASF happens. Collusion in private works to their advantage. The users are going through with the soft fork regardless so all the miners have to do is determine if they want to hash for those users or not.
Is it even possible for miners to actually mine UASF without signalling it and letting people know that they are mining it? It make some sense since no website have any charts or numbers that we could rely on.
It's actually far more beneficial game theory-wise for miners to not signal with their hashing power till after the UASF happens. Collusion in private works to their advantage. The users are going through with the soft fork regardless so all the miners have to do is determine if they want to hash for those users or not.
This makes sense from a "sekrit club" perspective but it seems highly unlikely that there is some sort of collusion going on that is getting enough hashing power to signal something like UASF without it being known at least slightly. 
