but I don't see how anyone could interpret 30.06 to apply to anyone other than license holders.
The point that concerns me is that 30.05 doesn't require any specific written notice, just written notice. So the iossue comes down to whether a 30.06 sign would also be written notice to a non-license holder. The argument you would have to make is "the sign said license holder and I'm not one, so no law broken."
That is a very technical argument. I think it has a chance of succeeding; but I sure wouldn't bet my own money that way.
FWIW, I tried to do some research on criminal trespass to see if there were any cases addressing this. Didn't find any; but some of the cases I did find were bizarre.