I am from Bayombong and havent heard about a tunnel being constructed. Maybe what you meant by an alternate route is thru san jose and maybe pass through a portion of pangasinan. i dont know the actual route, kasi nakasakay lang ako. From pangasinan, lalabas ka sa kayapa, nv then thru aritao or bambang. magtanong ka rin sa mga vehicles sa shell station. maraming taga cagayan valley na nagkakape diyan. have a nice trip!