As I understand, Indirect fire weaponry such as a Basalisk and Smart Missile systems are not required to check for distance. The VoT rule forces a model to make a spot check, rules for spotting require you to have LoS and models that indirect fire don't need to spot or have LoS.
Fluff wise, VoT removes the harlies from the players "mind". In the case of the smart missile systems, the computer still sees them there, but the pilot doesn't think there is anything there. He trusts his computer and continues to fire.
Of course you could go as far as saying that VoT doesn't allow the pilot to see the data on the computer, but I think thats a little far fetched.
We actually had an interesting discussion on this recently on these boards. Basically what we came up with is that RAW, even indirect fire units can't target harlies if they're out of the veil range. There is a little clause in night fighting, stealth suits, grey knight shrouding, and all other similar abilities that says indirect weapons just roll an extra die for scatter and take highest. The harlequin veil provides no such addendum for indirect weapons. It simply says that if they're out of range they can't target the unit. However, there's a whirlwind variant that lays mines, and that one can do it b/c is can target the ground between the models. Fury of the ancients and vibrocannons likewise can hit harlies because they just draw a line and don't have to target a unit.
However, as often happens, RAW is kind of stupid in this case.