I flew a Cessna 310 under FAR 135 carrying pax. Even though it had boots, hot props, and an alcohol w/s, it was not a known ice airplane. To be one, it would have had a vertical tail boot, wing root boots, and a hot w/s.
I flew it all over WV, VA, PA, NY, NJ, OH, TN and more 12 months a year under IFR and VFR. If there was ice you could not avoid, then you couldn't go. For example, if there were ice reports between 7 and 9, you cruised at 5.
If ice was to be a factor, the pax were scheduled in a known ice airplane. If I encountered unforcast or unreported ice, I used the equipment I had to get out of it.

I flew a 58 Barron under FAR 91 that was not a known ice airplane either. It did not have any boots at all.