When I recently had my boots replaced the kit from honda came with cable ties only according to Steve at HH this is standard practice. As long as they do the job I guess its an easy way to get it done and dusted.
Done my digging and 2.5 E 1 of the MOT manual states it's a fail if insecure. There's no mention of cable ties as a fail. I suppose therefore it depends on the type of cable tie used and how secure it is. I can't see any issues with a properly installed heavy duty secure cable tie.