Simon
IMHO - It all depends on the weather on the roads that you are expecting. If you don't plan on being in snowy areas then there are no rules but getting caught in a snowstorm could cause you problems with the Law....
Recently, Germany added new rules to their Highway Code. According to the law, motorists must have winter tyres (that bear the M+S symbol) if they are driving on snow, black ice or roads covered in frost.
If you are caught driving in these conditions without the appropriate tyres fitted, you are likely to be fined €40. This amount will be doubled if you are the reason for any delays to traffic. You will also lose one point on your driving license. (???)
I have a set of winter tyres, but for me it makes sense for the UK, but where you live.... a different story all together.
If you can keep out of snowy areas, a set of emergency would be a 'get out of jail free', if you get caught out, but if you are expecting to be on snow, then you need to seriously think about the regulations.