I'm not in a position to monitor Waukesha County but since this an analog system check and make sure your settings are for analog and digital or analog only (audio settings). I believe this a Motorola Type II system. If your BCT8 does not have the latest firm ware update you may have to alter the band plan. There was rebanding on 800 MHz band and for some scanners you have to alter the band plan to follow the trunking radio traffic. There is a Wiki page for rebanding 800 and new band plans. Not that difficult to do but probably won't recieve trunking system without the proper band plan.
P-25 Systems don't need a modified band plan as the data stream is sufficient to follow the trunking.
This link has all the info you should need in regards to rebanding and modifying the scanner band plan. I had to use the rebanding band plans to receive Indiana Safe-T Motorola Type II system. Once Indiana Safe-T migrated to P-25 the band plan did not have to be altered.
I know Milwaukee County and Waukesha County are cooperating on a new P25 trunked system Oasis. I don't know if Waukesha County has transitioned to Oasis. Not sure if you have programed Oasis which is P25 Pase I system. Here is a link to Oasis.
To be honest I've never done a firm ware update so I don't know if a firm ware update deletes the previous entries. I wouldn't think the firm ware update would affect the 800 MHz band other than not needing the band plan change. There could be other minor tweeks which might improve reception in the 800 MHz spectrum.
Most of the newer public safety trunked systems are P25 trunked systems so I wouldn't think the firm ware update would affect them.
This might be a good question in the uniden scanner forum.