In other words, we expect that students do have an incentive to minimize their costs (unless the subsidy program is set up in such a way to negate that incentive), though the fact that students use price as a proxy measure for quality in higher ed likely significantly dampens this effect.
To reiterate, carefully evaluate the goals and the design of such program, to maximize the chances for savings on health premiums and for increased employee efficiency, minimizethe risks of discrimination claims, and attract universal participation by all employees.