Regarding the BTL –it is accredited nationally by the US dept of education under –Association of Advanced Rabbinical and Talmudic Schools, Accreditation Commission (AARTS)
1974/2013/S2015-C—see http://www2.ed.gov/admins/finaid/accred/accreditation_pg7.html
There is another type of accreditation called regional accreditation which is what most grad schools require(most BTL granting yeshivas/schools dont have that because it requires a lot more general studies requirements, i believe ) — however depending on the type of school, area located , deals with local BTL granting schools, and other factors such as pre-required coursework and resume and high standardzied test scores — a student potentially can get into high level grad schools — and more likely in law schools.
Also most of these BTL yeshivas/schools have deals with local programs to accept some or most of the BTL credits towards transfer credit to that school to be completed there – and receive a regional diploma from that university