Engenius would work but it would require the following per station. Note the sites would be stand alone and do not act like cell or Companion sites.
1 Engenius base station & handset, 1 ATA2
The range on Engenius is great. But correct siting of the transmitters is ALL.
For Norstar Companion you will need the following:
MICS XC Software, 1 Base Station, 1 pwr supply and 1-2 two 3060 handsets. DO not use the 3050 handset. Each Companion base station supports two mobiles. Each base station acts as a cell site and calls pass off from one to another. Several Base stations may be co-located to create a cell site that supports many mobiles. With external antenna, the Companion has got pretty good range. Each base station contains two radios, each radio (not a mobile) has a port for an external antenna so you have a lot of flexability on how you deploy your RF pattern. You can make your own atenna from 'field tunable' motorola car radion antenna parts.
There is another product called ASCOM but I have no experience with this. It costs more than Companion.
Although Companion has been officially discontinued, there are still parts all over the country for it. I have deployed several and am satisfied with the quality (as long as the 3060 mobile is used). The 7316 works well enough and you can fool it into having more than 3 lines, the range is quite poor and not suitable for more than a small office. The 7316 is subject to mutual interferance from paging transmitters etc.
Another product called Mobicel works on a Cell site scenario. It's range is pretty good, the price is low and the handsets are fairly rugged with an NiMH battery. Each mobile can show up to 4 analog lines and intercoms between sets. There is no AA with this unit.
Voyager is like Engenius with better antennae systems available not just the one omni directional that Engenius supplies. Voyager has a Yagi directional that give one hell of a gain! There is also an AA in the Voyager unit so callers can choose the extention directly. Engenius and Mobicel have to go through ATAs or Analog Ext Modules with the AA in voice mail or CICS.
Hope some of this helps. ASCOM is supposed to be the up and comming thing but I think the expense will kill it.
PhM