[DTV]

Were there any other years when they did this?

For a long time, the late news during election campaigns was broadcast as 'News and Campaign Report'. In 1979, this included bulletins being extended to 30 minutes (rather than 25), with longer extensions from 1983, which could often be up to 50 minutes towards the end of campaigns. These bulletins often included bespoke branding elements, though new titles in 1987 are an exception. In 1992, they came from their own set; in 1997, they modified the regular studio to include a different backdrop and had an election logo in the middle of the studio (which meant they didn't do the regular opening/closing panning shots). (As above in Transmission's post).

This sort of thing died down a little come the turn of the century. In 2001, bulletins were only extended by 5 minutes and had no unusual branding, beyond the standard Vote 2001 graphics being used for over-the-shoulder overlays. I seem to recall them adding a little exploding X into the regular titles in 2005, but don't think they've done anything special beyond extensions in recent years (as well as coming from the election studio during the final week in a few elections).