Perhaps they are using a different repeater site? I have not taken a look at the license for changes, however I never heard them before, and now hear them daily, on 460.150, CTCSS 179.9, all over Chittenden and Addison Counties. In fact, they come in stronger than Williston, Essex, and Colchester PD, in most of the area I usually drive in. Whereas before a month or so ago, I never heard Derby unless I was much closer.
EDIT TO ADD:
I keep extremely detailed monitoring logs, and looking back, I never once heard Derby in this part of VT before 7/3/12, that is the day I began hearing them loud and clear all of the time. So I stand corrected, it has been more than a month or two that I have been hearing them so well. I will take closer note as to where I hear them and how strong the signal is. I have pretty much memorized how different bands are received without propagation, all throughout my normal travel area, so I will see if propagation appears to be a factor or not.
Try setting the frequency to CSQ. Most of the new EQ's have XTL series mobiles in them, and they are preparing for the switch to digital. I don't know what they are using for encryption, but I know that numerous agencies within Chittenden County are using DES-OFB over Motorola's DES-XL due to interoperability concerns between Kenwood, Motorola, and ICom P25 radios.