You cannot do a true simulcast setup with TRBO on the same frequencies. You'll have to have separate frequencies for each site.
You'll have to take this into account and it might be difficult getting enough frequencies to build out a large trunked system.
If you need a lot of talkgroups or a very dynamic system, Linked Capacity Plus is the way to go.
If you only need 3 or 4 channels, it would be very easy just to do IP Site Connect. You can also share talkgroups across the same frequency and timeslot if you really want to conserve equipment usage.
IPSC can be configured to allow for roaming for users so there's no worries on manually changing channels. TRBO is much more affordable compared to P25, but it's subscriber units are less rugged as well, consider your environment and user base when thinking this stuff over. P25 is also much more difficult and expensive to link compared to a simple IP linking done with TRBO.
You can also make a 3 site analog simulcast for much cheaper and have a dedicated channel and open your options up for use of most any conventional analog radio.
A little more details might help point out the pros and cons. How many people are planning to use it at any given time, how many channels are you hoping for, how much expansion are you looking for over the next few years. What's your budget, etc.
