I'll assume that the appropriate school/subtype (say the conjuration school) has been selected for spells. OSF works on one school or subtype, chosen at time of casting.
Orb of Fire yes, you'd be trying to cast the spell into the area (I think).
Wall of Iron, I'm not sure, if the Wall were laid down outside the field, then pushed over into the field, I think it would just be treated normally, however, if the Wall were laid down inside the field then, yes, you'd be trying to cast the spell into the area.
EDIT: Bizarre, it seems like it was supposed to be like a reduced power Antimagic Field, but not.