I recently set up a stream for Saratoga County Fire/EMS only (Saratoga County P25) using a $20 SDR dongle, LNA and a 12 element 800MHz yagi pointing at the closest tower site. I'm getting near 100% decode all of the time at this point. It's not impossible to do, but from my experience even with an SDS-100, you either have to be in the right spot to get a good decode or have a good antenna setup.
At my house I wasn't able to get anything on the SDS-100 even outside without a yagi hooked up and pointed at a tower site. Switching to the SDR dongle and a large 12 element yagi on the roof everything is great. That being said, driving down the road from my place into Clifton park further I would get 100% decode no problem with an SDS-100.