In my experience they can mostly be interchanged but you have to be careful which model you intend to take them from.
Example:
Seat
leon mk1 can use genuine - VW Golf mk4 alloys (98 to 2004), mk1 Skoda Octavia Alloys (98 to 2005), Audi A3 alloys (from 98 to 2003 only),
Seat ibiza Alloys (2002 to present) etc etc
Seat
leon mk2 can use genuine -VW Golf mk5 alloys (2005 to 2009), mk2 Skoda Octavia Alloys (2005 to present), Audi A3 Alloys (from 2004 to present), Seat Altea (all), Seat toledo (2005 to present).
Its all About the chassis change over year when the changed from the old type chassis to the new type, which all the 4 brands have at some stage and the main difference is that the bolt holes are spread further apart.