As 411A said planning stage of the flight and in-flight is different. When dispatchers planning a flight they must choose alternate which satify next higher approach minumum( If alternate has Cat II or Cat III you have to see Cat I minumum to choose this airport as an alternate) . When in-flight pilots always use charted minimums. No calculations for next higher or sth.
I have doubt about sth. For example if our crew doesnt have cat II or Cat III certificate and alternate has Cat II or Cat III. Should I look to Cat I minumum or sholud I look to non-precision app. minimums. Anyone know sth about that.