Tetra as in four? Given the antenna it makes sense... It's not an abbreviation but a name. TETRA is an abbreviation of Trans-European Trunked RAdio which is now know has TErrestrial Trunked Radio.
Given they work in different spheres and that context provides clarity, it doesn't seem a big issue. Further, it's a model name not the name of the device/system. It's like complaining that people could get confused between Windows Vista and Altavista (both of which no one should think too hard about lest the nightmares return).
