It depends on why the drug is not on the formulary. A self-admininstered drug not on the formulary would not be covered before or after the MOOP has been met unless an exception has been granted. Each plan is required to have an 'exception process' (aka appeal process) to have a drug added for that specific member. That does not mean the drug will be added.
Intravenous drugs that must be administered in an office/clinic setting fall under the medical benefit, not the drug benefit, and often never appear on the self-admin formulary. You need to contact the plan to see which of these are covered. If covered, then it's like any other medical benefit that is paid after MOOP if in-network.
Challenges of Reimbursing Through the Medical vs. Pharmacy Benefit | Biologic Specialty Pharmacy