I've been out of the railroad monitoring scene for awhile, but I was real big into it back in the years immediately following the UP/SP merger. I gave it another shot on a bored whim a few months ago, and it didn't sound like much had changed in 15 years or so, so here's my somewhat-dated but (apparently?) still relevant input.
UP is big on recycling frequencies throughout the state. A lot of their road activity can still be found on predecessor road frequencies but from '97 through '98 they licensed a bunch of new frequencies under the predecessor road's callsigns. Give these a listen if you're in a UP-served area:
160.41 (old Missouri Pacific)
160.47 (old Missouri Pacific)
160.515 (old Missouri-Kansas-Texas)
160.74 (can't remember which predecessor road used this one)
161.55 (old SP Road Ch. 1)
160.32 (old SP Road Ch. 2. Used extensively in Texas on former SP lines)
161.4 (old SP yard channel. Listed in some places as a police frequency; never heard 'em, even back when SP still existed)
161.28 (old SP yard channel, used at Strang Yard in La Porte)
160.665 (new post-merger channel)
161.445 (new post-merger channel)
160.365 (new post-merger channel)
160.875 (new post-merger channel)
160.995 (new post-merger channel)
160.77 (new post-merger channel)
161.43 (new post-merger channel, used at Englewood Yard in Houston)
160.44 (new post-merger channel, used at Englewood Yard in Houston)
160.8 (old SP PBX channel)
160.95 (old SP PBX channel)
160.605 (old pre-merger UP PBX)
As far as the police go I can only vouch for what goes on in the Houston area but they've never been big radio users. The old 160.38 repeater is long gone, and not all of the vehicles have 800 radios (each road has a talkgroup on 2318) or even have radios installed at all.. or are even marked as police vehicles. The last UP "dick" I ran afoul of was in a regular ol' Ford pickup with a HT1000 listening to one of the yard channels which he was not dispatched over.. he was just listening in. For the most part they're dispatched individually by cellphone, or they hang out in the yard office until needed somewhere.