Some people have found that the Uniden x36 scanners can work, at least to an extent, with P25 simulcast (LSM) systems such as the Regional Wireless Cooperative (RWC) and TOPAZ RWC. However, unless you can find a "sweet spot" to place the scanner in, or use an outdoor directional antenna and play around with the best direction to point it in, your decode percentage won't be 100%, and you will miss transmissions. Then again, you may not get much of anything from them if you're in a bad spot.
The SDS-100 has had mixed reviews across the country, as well as here in the Valley, in regards to its performance with LSM systems speficially, as well as its general performance in certain enviroments, especially electrically noisy ones such as around computers, as well as in high RF enviroments. Some have had excellent results, some have had poor results. Some of this may be due to manufacturing variables in the hardware being used, and some of it may be due to Uniden still tweaking the firmware. (I myself don't have either of the x36 scanners nor the SDS-100.)
Without buying and using the radios, you won't know what will happen.
However, to answer your questions:
1. For what you want to listen to, yes, the main sites are all simulcast. There are a few single site Intellirepeaters, however, very little main police or fire comms are carried on them.
2. For Scottsdale PD, you want RWC Simulcast H.
For Tempe PD, you want RWC Simulcast F.
For Chandler PD, you want RWC Simulcast C.
For the Phoenix FD Regional Dispatch Center EMS calls, you can pick whichever simulcast is closest or gives you the best reception, as they are carried on all simulcasts except Simulcast A. (Fire & Hazmat calls are carried on the Phoenix FD RDC analog NFM VHF channels.)
For Mesa PD, Gilbert PD, and Apache Junction PD, you want the TOPAZ RWC Mesa Simulcast.
For the Mesa FD Regional Dispatch Center, you want both the TOPAZ RWC Mesa Simulcast and the Mesa FD RDC analog NFM VHF channels.
3. You only need the control channels and alternate control channels.
4. Even if you do experience issues with the LSM systems, there are other things to listen to. DPS is on analog NFM UHF channels, as well as on a non-simulcast P25 system, alongside ADOT. (Don't discount listening to ADOT. The ALERT emergency response units can be very interesting and informative to listen to when it comes to incidents on the freeways.) The Maricopa County Sheriff's Office is currently using an 800 MHz mixed analog/digital trunked system, that is easy to hear. And the county DOT has its own emergency response unit, called REACT, that works with both MCSO as well as many PD's, and has assisted ADOT ALERT units in the past. The county is working on installing a 700 MHz P25 (probably Phase II) simulcast trunked system, but it'll still be awhile before it goes live. As mentioned above, both Phoenix and Mesa have analog NFM VHF channels, and there's also Rural/Metro FD, which covers county islands in the East Mesa area, as well as other areas around the county, and in the San Tan Valley area of Pinal County. The Salt River and Gila River (and Ft. McDowell) Indian Community PD's are encrypted, but their fire departments can be monitored.
If you go over to the Arizona forum, I'm sure you can find locals to you who can meet up with you in person and give you some pointers. I myself am on the other side of the Valley.
John
Peoria