Unaffordable and unnecessary. The existing ex-LNW route from Liverpool Lime Street to Leeds City via Chat Moss and Standedge is adequate, but needs full electrification and upgrading east of Stalybridge as per TRU. 2 fast tph would be adequate, providing they are sufficiently long, so an expensive tunnel is overkill. TPE are about to downgrade this service to just 1 tph! Additional semi-fast services would run between Manchester and Leeds, as now.
Better use needs to be made of existing capacity by simplifying routeings, together with conversion of some more local rail lines to Metrolink and mothballing the problematic Ordsall curve, before considering expensive tunnelling. Trains on the Standedge line not proceeding beyond Greater Manchester should terminate in Victoria platforms 1-2 (for stopping trains only, as these platforms are short) or Piccadilly platforms 1-3.