A South Fork railroad service that could accommodate those commuting into East Hampton Town for work, a service that has long been discussed and was instituted for a short-term trial in 2006, is feasible, Long Island Rail Road officials agreed at a meeting last week with the East End’s state, county, and local government officials. Agreement on new services and train schedules, and a plan for their implementation, could be finalized as soon as next month, with a target start date of 2018.