According to this[1] definition, a confidential source is a PERSON who provides information. If this is so, then the judge that approved the warrant was actually tricked: a person providing information implies that the information may be volatile (the witness may have seen something by pure luck), and on top of that it also means that the information was obtained through a legally sanctioned way (ie, a witness and/or a confession). If they used a word that defines a person to identify something that was not a person, then yeah, there was some deception involved.

If I read the article correctly, what happened is that the police obtained information in ways they apparently weren't allowed to use (unconstitutional surveillance), and then hid this fact under the pretense of a supposed person giving that information. This is all kinds of wrong and, among other things, voids those warrants.

[1] http://definitions.uslegal.com/c/confidential-source%20/