Forgive me for insisting that technical curiosity take a back seat to the real-world medical needs of people. But I will insist. This is a real problem, not an experiment nor a business decision.
Indeed, that is Bell's problem that it MUST solve. If the transition has broken backwards compatibility (to use our lingo), they must fix the breakage. Their current digital-to-analog solution may work for many users (such as my landline) but clearly isn't sufficient for Karen's needs.