Thomas and Betts invented the Tywrap and I looked on their site for the installation instructions but that document 404's
I have a question into the support desk.
I did find this in the FAQ
Which of your cable ties are plenum rated?
All of our UL listed standard Ty-Rap brand cable ties are plenum rated. This includes the colored ties. The black weather resistant ties are not listed for plenum applications. The Catamount brand ties are not listed for plenum applications.
So I guess there are U/L listed tywraps but you would have to see the bag. If these are no name Chinese ties, who knows?