Navi won 8 out of 9 Train maps this lineup, only losing 6-16 to Astralis at Blast Pro (won 16-8 against them last time they played Train), Fnatic this lineup won against NiP and lost against G2. Nothing points towards Fnatic being favored on the map, but granted, they have barely played it (which imho isn't exactly a good thing). No question that NaVi is a quality Train team at the moment.
Fnatic 3 wins out of 7 matches on Overpass this lineup, NaVi 4 out of 4, including a win over Fnatic. How is this Fnatic favored?
Dust2 definitely close and I could see the case made for Fnatic too, definitely better stats on the map. Definitely the one I am most unsure about I will give you that.
Fnatic is 3 wins out of 7 on Mirage during EPL losing to Forze, FaZe, Big and OG, generally unimpressive Mirage stats, NaVi played the map well in Katowice (but did lose to Fnatic, yes), got more rounds against FaZe. I could also see the case made either way here but I honestly do think that NaVi has a more impressive resume on the map at the moment, better lineup winrate too.