I'm not sure I have ever heard this word in Gaelic. I have only heard TBh. I did a Google search for telebhisean bbc and tbh bbc as I thought the BBC should know and I got 99.7% of the hits for TBh.
Gaelic is an old language, television is a new word. I get the feeling that a lot of the newer words are somewhat improvised in translation to Gaelic. Rèidio is also similarly handled. As well as coimpiutair.