The below code will evaluate if a message that contains the word "Twitter" in the channel that you specify, is from a specified bot and from only selected users.
If that is the case, it will send an exact copy of the message to your selected channels.

You do have to manually set your selected values in the script.
It's explained below and you have to do this only once or manually adjust it over time.

Code:
on *:TEXT:*Twitter*:#twitter-message-channel:{

  var %selected-bots = Bot
  var %selected-users = seanturner70,SomeselectedUser,OrAnother
  var %selected-channels = #channel1,#channel2,#channel3

  if ($nick isin %selected-bots) && ($2 == Twitter:) && ($3 isin %selected-users) && ($4) {
    msg %selected-channels $2-
  }
}


In the first line: #twitter-message-channel

Then the 3 variables:
%selected-bots = Bot
%selected-users = seanturner70,SomeselectedUser,OrAnother
%selected-channels = #channel1,#channel2,#channel3

It should then be ready to go.

If you want, you could also adjust the message that you 'broadcast' by simply changing the line that starts with "msg".
Like: msg %selected-channels Twitter update! $3 just said: $4-
You can add colours by hitting CTRL+K (inside the mIRC Script editor) and type the number that corresponds with the colour.

I hope it works, didn't have mIRC available atm smile