So in the case of Steal Equipment, would it "reset" the binding on the new attachment or can he opt to keep the current spell since one is present?
It seems to me that the attached spell should be destroyed and the caster of Steal Equipment should bind their own spell to the wand. My reasoning is kind of hard to explain, but I'll do my best to make it comprehensible.
1) Stealing the equipment should give you the abilities of that equipment. The ability of a wand is to allow you to cast a spell you know, and have thoroughly studied, multiple times, instead of just once. So to have a wand that now lets you cast an unfamiliar spell seems wrong to me from a flavor standpoint.
2) The implications of stealing the spell seem weird to me. A wand lets you change the bound spell for 3 mana, returning the previously bound spell to your spellbook. So, would you then get your opponents spell in your spellbook because you took his wand? Just another thing that seems a little illogical.
Obviously, there's not a lot of rules support in those arguments, as there is no precedence for this issue, hence the discussion. That's just how I would rule it if it came up in a game and there was no official ruling.