Fire and police dispatch are in the clear. What scanner are you using? I used to monitor the system with a BCD436 and had to set the squelch to zero for it to stay locked on to the control channel. Reception seems to drop off outside city limits for scanners. I use a Unication G5 which gets better range and has no problem with the control channel.
You will not pick up the Bartlett system from Collierville. Way too far. It is good for 5 to 10 miles outside city limits. You get Millington, Memphis because they are on a county-wide system. Bartlett has their own system.
It varies where you can pick it up. I have a Unication G5 that does an awesome job of receiving and decoding. The sites are Yale/Brother (the original site for the old analog) and one in Brunswick area. The antennas for the digital 700 system are lower and have less coverage than the original 800 analog. The out of coverage alert on the G5 goes off when I get to Wolf River headed south on Germantown.