Volvo itself claims it is (or can be), especially for the (euro only?) B230FB (531 head, VX3 cam as factory eqpt). I'm currently changing the head on one, and as far as I can see the valves do not at any point protrude below the head surface, nor do the pistons protrude above it, so I'd say even this is a non-interference design.

I guess that perhaps with even more radical cam designs or milling the block down to or beyond its limits it could be turned into an interference engine, but personally I don't worry too much about it. This of course does not constitute legal, mechanical or maintenance advice, this message provided for entertainment purposes only, not liable from any damage resulting from your application of the entertainment contained herein to any actual engine, etc etc.

Bram