Does your insurance company have a website? If so, they probably have a list of prescription meds they cover. Or you can call their customer service and I'm sure someone there could tell you whether or not VSL#3DS is covered. If VSL#3 DS isn't covered by your insurance, ask your doc to contact them and both you and your doc can lobby to get VSL#3DS added to your formulary. The odds that your insurance will go for it are slim, but it never hurts to try. If your employer has PayFlex available I know that they will reimburse you for VSL#3 as long as they have a note/prescription from your doc saying you need it.
Good luck with this. Insurance can be a hassle, but every once in a while you'll get someone who actually cares and is willing to help out (beyond the rote answers they get from their computers).
36 y.o. male
Diagnosed w/ UC in May '06, had symptoms since '99
Meds & supplements: VSL#3, Lialda, Allegra, multi-vitamin, buproprion, fluoxetine, and vit E, D, zinc.
Started LDN: 1.5mg for now