ISM Band

According to a lot of pages the ISM Band filter must be removed to
operate
Open BTS.

In Australia, we have mobile carriers operating in the lower half of the
900mhz ISM band - and only 918 - 926mhz is unlicensed. Is it possible to
have Open BTS only operate in the unlicensed spectrum - and if so, what
limitations would this place on it?