Are anti-anxiety meds helpful in combination with cbt for insomnia?

Very Possible. Insomnia is caused by many many things. Thinking about biological and psychological interventions is often helpful. Anxiety meds are helpful in the short run but maybe not long term. Cbtcan be very helpful to look at various cognitive and behavioral components which are contributory.
For Some. Anti-anxiety medications have their positives and negatives. The most commonly used are the benzodiazepine class. They may not be indicated and usually not idicated for long term use as they can cause rebound insomnia (insomnia that comes back after you have stopped). Under the care of a specialist however, cbt can be used with medications.