The risk of a IBD infection increases if you bring in new boas and house them in the same area with your pythons. IBD typically affects both pythons and baby boas very quickly. If you've had a few months go by without any issues with your current collection, then you're most likely safe.
If you practice standard quarantine with a new baby boa...and it proves to be healthy after you've owned it a few months, then it is probably fine to move to the same snake room as your pythons.
If you bring in an adult boa, however, there is no quarantine long enough to guarantee the animal is not carrying IBD. They can be carriers without symptoms for a very long time and you simply may never know.
If you MUST house boas and pythons together, you can still mitigate your risks by making sure they never share prey items, water bowls, hides, etc. The exact methods of transmission for IBD is still not certain, but most experts believe it is by contact. A snake can contaminate refused prey, or cage furniture. Mites can also become contaminated by crawling around on one snake's mouth, then moving to another snake's enclosure and crawling around. Always handle your animals separately, and wash thoroughly between each.