On to the question...
You'll need a scanner capable of receiving digital trunked systems. Macon-Bibb and Houston are on different, digital 800MHz trunking systems.
That said, you'll have to pick Uniden or Whistler brand. I've owned a lot of both brands and know the Uniden BCD436HP or BCD536HP will work for you. Also, the Whistler TRX-1 or TRX-2 will work. It's your preference on scanner form factor, programming software, features, cost, etc.
You can find used Whistler and Uniden scanners, with different model numbers, that will do the same thing. They're just older, but they still work. I have had a few of those, too.
A third option is Software Defined Radio (SDR). Like Uniden and Whistler, there's a huge forum on RR that gets in what it can do, etc. Cheapest option going, unless you get handed a free scanner. Like $20 cheap, but you need a laptop/desktop computer to pair to it.
The fourth option is a Unication pager/scanner. I love my model 5 and it works better than anything readily available (today). It's more like a public safety radio but does best in simulcast situations.
For me, I like the Whistler scanners best and own the TRX-2. It's my main scanner in the car and on vacations. Otherwise, you won't go wrong with the Uniden BCDs. Both companies are hinting at a new model this year (Uniden's nearly released; Whistler's is a Christmas present).
