Scart via VGA is unusual but not totally unheard of and the cable is only 13 quid so there's probably no sync mixer in there.
I would just send an email to the makers asking what the pinout is in SCART mode, failing that buy the cable and buzz it out with a multimeter.
If you can find that bit out yourself I'll draw you a wiring diagram to connect it to an a520 with power
