In Connecticut the Plaintiff is required to file a lis pendens in the land records when the foreclosure action is initiated. It serves two purposes. It gives notice of pending litigation, and it also binds subsequent encumbrancers of the property by the judgment if they were not made defendants to the action. If they record subsequest to the lis pendens, they are required to intervene in the foreclosure action to protect their interest. Otherwise they are foreclosed.

In order to claim the jurisdiction of the federal courts there must be either a federal question at issue involving the U S Constitution or a federal statute, or there must be complete diversity of citizenship among the litigants coupled with the proper jurisdictional amount at issue.  If the lender is located in one state and the homeowner is in another, possibly that is how they are doing it.