I'm also wondering:

1) How did we know that the two who joined our club
were ICG employees?

"The check for their memberships was an ICG check."

2) Why did someone have to ask on the bb if anyone
from ICG is a club member?

"It is not a past practice of the club to arbitrarily publish information about members. If this was done in this case it could have been construed to be bolstering one side of the debate, or the other, depending on how you viewed it. As long as I was asked the question, it was answered, but it would not have met policy to publish this fact outright."

3) Would we have not known of this if nobody asked?

"No you probably would not have. (see above) Also note that if the members had indicated that they did not want their information published, then even if someone asked, no one would not have known."