According to this article, the US Capitol Police are beginning testing of their new radio system:
http://www.rollcall.com/news/capitol_police_begin_testing_long_delayed_radio_upgrade-228775-1.html
The article states that they are testing system coverage of portable radios in each room of the Capitol building.
The system was planned to be a P25 VHF trunked system, with encryption being likely. Here is what information we have for frequencies from the original proposals of the trunked system. This list shows proposed trunked system channel, repeater transmit frequency & input frequency;
1 - 169.5750 / 162.2500
2 - 169.8375 / 162.6125
3 - 170.1375 / 162.8000
4 - 170.3750 / 163.1625
5 - 170.5750 / 163.6000
6 - 171.0000 / 164.0125
7 - 171.4125 / 164.3250
8 - 171.7875 / 164.6125
9 - 172.3875 / 164.8125
10 - 172.6875 / 165.0375
11 - 172.9625 / 165.5375
12 - 173.1625 / 165.7750
13 - 173.4750 / 166.2250
14 - 173.8125 / 166.4250
Details of this new system (System ID, WACN, NAC, etc.) are still waiting to make it to the radio forums, but I will update when information becomes available.