First: let's be clear with the terms.  by definition, a women is pregnant as soon as conception happens.  Contraception, by definition, prevents conception from happening.  

A women does not become pregnant when implantation happens.  She is already pregnant when that happens.  This means that a drug that prevents implantation is by definition an abortion inducing drug--not a contraceptive drug.  

Second:  Any institution that operates under the name "Catholic"  cannot provide services that are contrary to the Catholic Faith.  The only way to change this would be if the institution becomes secular.  Given that the US Constitution is supposed to protect the Church from government intrusion, we should not have to do this and we will refuse to comply with any law that forces us to go against our Faith.