Unless their plans have changed, the leg of the wye which will be installed is from the Corning Secondary southbound to the Auburn Road eastbound. This has been on their "any day now" list for at least 5 years, and at one point there were bundles of new ties laid out for the project along the north side of Border City Road.
Many factors affect planned trackwork, including budgets, derailments, new customers, urgently needed repairs elsewhere, available manpower, etc. I expect that at some point the project will likely be accomplished. Just when, I would not bet money until you see a train actually using it.