The only orders I can find are here: https://www.legislation.gov.uk/all?text=%22B95%22%20%22northern%20ireland%22

None of which refer to the B95 west of the Greystone Roundabout, let alone Founatin Hill. Unless anyone can think of another search term that might bring up something else. My hunch is that any legislation related to the B95 around the time that the Fountain Hill dual carriageway was built probably predates anything now availablie in the digital domain.