Yes, just dug up the service change list.
X5 was formerly the 15A
X15 was formerly the 15 (these literally were just a change of number, absolutely no timetable or route change otherwise)
X45/X46/X47 were formerly the 45/46/47 and the difference was that the express versions were non-stop from Metrocentre to Newcastle.

http://web.archive.org/web/2020103021481...uly-373932

(this was at the same time they commenced the short-lived extension of the 33 to East Herrington).

For the 15/15A, would it not have hurt to just supplement them with a truely limited stop service if they really wanted an Xlines route round there?