I always thought 33.80 or the repeater for it 460.625. However, I think I heard otherwise a while back. I'll tell you if it works.
Oh. I know I hear DTMF tones on 33.80Mhz. I think they send the DTMF tones out for the cyclone in Londonderry. However, I don't know if that is how they activate the TMI sirens.