  We prove the full covariance of the heavy-to-light weak current matrix
elements based on the Bakamjian-Thomas construction of relativistic quark
models, in the heavy mass limit for the parent hadron and the large energy
limit for the daughter one. Moreover, this quark model representation of the
heavy-to-light form factors fulfills the general relations that were recently
argued to hold in the corresponding limit of QCD, namely that there are only
three independent form factors describing the B -> pi (rho) matrix elements, as
well as the factorized scaling law sqrt(M)z(E) of the form factors with respect
to the heavy mass M and large energy E. These results constitute another good
property of the quark models \`a la Bakamjian-Thomas, which were previously
shown to exhibit covariance and Isgur-Wise scaling in the heavy-to-heavy case.
