OSTN02 is a unique form of transformation between the Projected Coordinate System, British National Grid and Geographic Coordinate System, ETRS 1989. Defence Geographic Centre, Steve Baker, created an NTv2 format of OSTN02 which is used by many GIS Systems and Ordnance Survey has approved its use and indeed offers the download of the .gsb file from its website.
EPSG have registered these transformations for conversion between Geographic Coordinate Systems, OSGB1936 and ETRS 1989 (EPSG::5338), and OSGB 1936 and WGS 1984 (EPSG::5339).
These transformations are now included at Version 10.1 and 10.2 although one still has to download the .gsb files from the Ordnance Survey and place them in the ..pedata/ntv2/uk folder.
As this is included in projection engine at 10.1 and 10.2 is it possible for Esri to install the gsb files and make use of this more accurate transformation in AGOL than the current Petroleum one (EPSG:1314)?