You can. I have set up DSD+ with a 9.99 USB stick, SDR Sharp and verified it decodes standard mototrbo. I imagine on a trunk system you'd have to put in each frequency. I don't know if Unitrunker will track a mototrbo system but if it does that program works supposedly with the dongle and DSD+ to trunktrack trunking systems.I have read that one can also use software like DSD+ (Free) and either a scanner with a discriminator tap or a dongle (about $20) to listen to DMR/MotoTRBO .
I think there is a separate Forum on this topic here at RR on how to do this and how well it works.