I agree that, as far as we have religious freedom, we cannot enact any law for religious reasons. Everyone can do whatever he likes unlless he harms other people or Nature.
Regarding New Year, if celebrated as a civil holiday, I don't see the problem with Jews and Noahides. Anyway, even if there is a problem, no Goyshe govt. can forbidd Jews to take part in such parties. Most Goyim don't adhere to the Halacha of who is a Jew, how can they enact a civil Law especially for Jews? Who is a Jew for them??? An Hallachically Jewish person?
That's why Let-be-land dropped the clause which forbade us to establish diplomatic relations with countries which allow intermarriage between Jews and Goyim in 2004. The problem was: How can a Goyshe country decide who is really Hallachically Jewish??? How can we demand them to distinguish between someone who is Jewish according to Hallacha, and a Goy who considers himself Jewish because his grandmother converted by the reform, and the rest of the family are real Jews?
Anyway, in case a Jew or Noahide wanted to celebrate civil New Year, they should do among themselves. Parties organised by non-Torah observant Gentiles are often dangerous and can lead to intoxication, immorality, driving careslessly and so on. Better stay away from these parties!!!!!!!