This is a new twist for me to hear about.
In Canada, insurance companies usually only refuse to pay to raplace teeth that were congenitally missing or extracted before the patient was covered by their companies plan. They use the,"Pre-existing Condition" Clause to justify this. Some Dental Insurance policies do not allow or cover, "Major Restorative", dental work. Major restorative usually includes, posts, dentures, partial dentures, inlays, veneers, crowns, fixed bridges and implants. So, if there is no major restorative coverage you would not be covered for replacement of teeth.
If I assume your plan was comprehensive, you should have some major restorative coverage and therefore should have some coverage for tooth replacement.
It may be worthwhile to review your plan details and then call the company. If you are not happy with what they tell you ask for the contact information of the companies Ombudsman office and write them a letter.
Cheers,

Mike