Thank you for the replies. Maybe I was a little too short on information the first time.
The engineer is referencing a generic statement in the spec about all materials being UL listed (not approved, sorry for the confusion). We are using the same hanger wire that is used for supporting ceiling grid and light fixtures. He is fine with those because he believes that the wire is UL listed for those applications. He's asking me to provide some reference that it is listed for the application of bundling. Our guys that have been here for 30 years have never heard this questioned before. Any advice on where to search for this listing?
Otherwise, we're reworking with UL stamped zip ties.