After April 25, 1996, all major modifications and extensions to existing FMS systems in the 1850-1990 MHz, 2110-2150 MHz, and 2160-2200 MHz bands will be authorized on a secondary basis to ET systems. All other modifications will render the modified FMS license secondary to ET operations, unless the incumbent affirmatively justifies primary status and the incumbent FMS licensee establishes that the modification would not add to the relocation costs of ET licensees. Incumbent FMS licensees will maintain primary status for the following technical changes:
47 C.F.R. §101.81