Yes. As per chapter 7.2, you would use M for billing ICH members (interclearance), but you might also use M if billing an ACH member using MITA (ICH) rules. Not sure if you do this, but some ACH carriers have bilaterally decided to.
For direct billings (e.g. an airline joins SIS but isn't part of the ACH or ICH), you would use B (bilateral).
In your example of "removed from membership" (or voluntarily leaving), you would probably use B (as per above). If it's a case of suspension (nonpayment of bills. which I understand the ACH does very infrequently), I would recommend that you continue billing with the SMI of A (or M). This will still flag the invoice for settlement, and your claim would be logged for any legal or bankruptcy claims. I don't know the specifics, but the ICH (and presumably the ACH) do this today with suspended members, in which you continue to submit your claim, and the principle will remain the same.
Finally, N is for no settlement at all, bilateral or otherwise. In sampling today, you send a listing of coupons which looks very much like a standard Pax invoice (coupons, taxes, a total, etc) which is purely information, and where there is no settlement at all. N is used for this, and similar occasions that may occur in the future.
Hope that helps,