Success! I just went through this in the past week. My doctor sent a prescription for 7% Saline to my local pharmacy. They tried several ways to get it approved and could not. I remembered reading an earlier post on this site regarding this issue. Medicare Part B does cover saline for nebulization, but it must be submitted specifically under the DME (Durable Medical Equipment) section under Part B. I told my pharmacy about this and they informed me they work with Part B - but not the DME part, as they do not supply other DME items, such as nebulizers.
I then had my prescription transferred to a pharmacy that supplies meds and DME items and -Success - the saline was approved under my Medicare Part B - DME coverage.
I hope this is helpful and others who have hit similar roadblocks find success as well!