Scanners are not going to work for you, my friend. No scanner on the current market works with TRBO at all. MotoTRBO is a digital mode (also called DMR, the standard it conforms to) sold by Motorola, and Capacity Plus is a trunked radio system (good term to research) that uses that digital mode.
The two options for monitoring MotoTRBO at all are a MotoTRBO subscriber radio (such as the XPR 6550) or decoding software (such as DSD+).
A subscriber radio is the most functional way. I've never programmed one to follow a Capacity Plus system without transmitting on it (transmitting on an unauthorized system is a BIG no-no), but I do hear it's possible, and it will follow conversations as they jump between channels (see
Trunked Radio Systems - The RadioReference Wiki for further). The downside is, proper TRBO radios cost good money, and the TRBO software for programming costs a pretty penny too.
Using a decoder program is much simpler and cheaper. You only need a radio that will provide a
Discriminator Output either via a tap or directly from the radio (available in newer radios like the PSR-800), OR a software defined radio like the ultra cheap and effective
RTL-SDR USB dongle. There are large numbers of instructions online (such as at
RTL-SDR.COM) on how to get this set up, and this will decode TRBO fairly well depending on the speed of your computer, signal strength of transmissions, etc. The one downside to this is that it does not track trunked systems like Capacity Plus systems. You can get around this by manually changing channels if you have fast enough fingers, but you will not likely catch all of every conversation you want, and may hear some other stuff you don't want.
Upsides and downsides to both ways of doing it. Neither is perfect - one is flawed by expense, and the other is flawed by technical shortcomings.
