but it does mean that when the airport goes officially "CAT2 / low visibility procedures" in the ATIS (e.g.
this trip) you can legally land there
It might be worth qualifying this. An ATIS advising you the airport is operating CAT II LVP does not mean it's illegal to land there. The LVPs refer to ground movements (eg. using the CAT II holding points). The RVR may be varying around the CAT I minima, and the airport wants to be operating CAT II LVP so that a capable aircraft can use CAT II. But, that doesn't mean a CAT I operation is illegal per se. The controlling factors are the CAT I minima wrt RVR as reported by ATC during the approach and the DA.
Of course, if the ATIS 50nm out is reporting CAT II, it certainly is prudent to divert to an alternate with better wx. But RVR can change a lot in 15mins.
brgds
421C