On the subject of lying, biblically the purpose of the act determines whether it is wrong, and in fact whether it should be called a lie or not.
It is odd that I have not heard anyone mention the case of Elisha in this issue. It was really a "These are not the droids you are looking for" scenario: he stood in front of the city of Dothan, and said "This is not Dothan, I will take you to Dothan." and took them to Samaria: and God supernaturally made an army believe it.
Another time when God aided in subterfuge was Husham: he pretended to be Absalom's friend and to give him counsel against David, and the Bible says that God had appointed that his subterfuge would prevail (II Samuel 17). Then there was the time when God made people hear an army that wasn't there, and the time when Jesus appeared in another form, for the express purpose of making his disciples think he was someone else (apparently only to have a better talk with them).
Something to note is that while the Bible talks of lying a lot, none of these examples are called lying. I believe biblically the accusation of lying should be reserved for the intent to do wrong: "A lying tongue hateth those that are afflicted by it; - Proverbs 26:28" does not reasonably apply to anything else. Withholding knowledge someone has a right to would fall in this category whether one said something untrue or not (in Hebrew the connotations of "lying" have to do with failing, disappointing, and proving untrustworthy).
I can see that God might not have a big problem with lying in matters of war, when you're deceiving someone in order to justly kill them. But aside from that scenario I would step very carefully about justifying lies. Lying is condemned in extremely strong terms in the NT. And people have a very good ability to fool themselves that their lies were for a 'good reason' or 'no big deal'.