SDR hardware and software can function in a manner similar to a scanner - you program frequencies into the SDR software on a computer and then it'll cause the SDR hardware to scan by hopping through the frequencies it's being told to tune by the software, sure. But, if you're expecting to be able to do the same things with the same level of ease you can with a physical scanner you can forget that right now.
Now, I'm not saying it can't be done - I'm not trying to scare you off from it, I'm simply saying that it can be done but you're going to have to put in time and effort to get the tools that you need together (hardware and software) and do the research and put the pieces together till you end up at a point where you click or press a Start or Power button and voila, you hear stuff you were hoping to hear.
It's more complicated, takes more time, and depending on your expertise with using software in general and reading instructions (both as part of manuals or user guides and also at forums like RR) with a decent level of comprehension, it can prove to be a frustrating experience for some people. I'm not saying it's not possible since obviously SDR is gaining in popularity every day but what I am saying is it's just not like using a physical scanner, at all. There's no piece of software out there that can or does take the SDR hardware which acts as the tuner and allows you to do all the same types of things with it in an easy point-and-click manner or method.
There is a built-in plugin with SDR# (the most popular SDR application) that can work as a frequency database manager but it does not provide scanning ability of any kind. There is an available plugin you have to add yourself called the Frequency Manager Suite which offers the frequency database manager, a plugin manager, and a scanner metrics tool for data analysis making it one very powerful (but still limited in functionality) addition for SDR#. It's not an easy point-and-click tool either but it does come with several PDFs as the author has provided some very well laid out documentation.
So in the most basic sense yes you can use SDR# with that plugin and an SDR device to program frequencies and then scan them, but it won't be an experience like it is with a scanner as there's a lot more to making it functional than doing the same thing with a physical scanner.
As for P25 Phase II (that's Phase Two), there is only one computer-based solution to monitor that type of digital format at the present time and that's using OP25 which is a Linux-based tool (it requires Linux as the operating system and it must be compiled on that machine along with some other things in the process). It's far more difficult than most people are willing to go but it does offer the only possibility for P25 Phase II monitoring on a personal computer at this time.
There's hope that at some point DSD+ - the most popular digital speech decoder which is a Windows-based application - may add P25 Phase II support but it remains to be seen if the developers are able to add that format at some point in the future. DSD+ can handle P25 Phase I (the most popular digital format in use worldwide), DMR/TRBO (gaining popularity with small businesses and some law enforcement), NXDN (popular with railroad operations, casinos, and small businesses as well), and several others like ProVoice which just became available on the Uniden line of digital capable scanners (only a few models at this time).
So, SDR is growing and gaining ground fast but it's still not necessarily an easy thing to get into or get a grasp on if you're only used to using physical scanners for a long period of time. That's not to say that using SDR hardware and software can't or doesn't provide some awesome capabilities, however, because it does - it's just not a very simplistic thing to get functional.
But that's why this place exists - to provide info and share it with others.
