I have a Pro2006 and it's unaffected by any broadcast or other strong transmitters, like a professional 2-way radio, when practically all other scanners loose sensitivity and needs a FM trap filter or other filters. It is the sum of all signals that matter so if getting rid of one of them could help to not make them reach the scanners overload level. I guess Pro2004 isn't of the same quality as a Pro2006.
The Pro2006 isn't as sensitive as most other scanners, at 0,5uV when others are at 0,25uV, so it depends of the interference level from the antenna which scanner that will work best. No interference and most other scanners receive better but close to a high power transmit tower and the Pro2006 will be superior in reception.
/Ubbe