Seen also at begin of '''R-Typeee.dsk''' ("stereo soundtrack" message's picture), and seem also used in a lot of recent demos as "flipping lace" effect.
Scanline is also used just at begin of '''Pinball_Dreams__PREVIEW.DSK''' (eagle draw) - in fact I've got a doubt here, it seems more about a problem of HSYNC edge choice of alignement here.
[http://cpc.sylvestre.org/technique/technique_identifier_crtc.html Les Sucres en Morceaux - Amstrad CPC - Identifier les CRTC]