I'm an HR Generalist and handle FMLA administration for about 2000 employees.
but, it's my understanding that FMLA does not protect your pay, it only protects you to have a job when you return
FMLA does protect your pay. Upon return from FMLA, an employee must be restored to his or her original job or to an equivalent job with equivalent pay, benefits, and other terms and conditions of employment. Courts in the past have held that not only does this pertain to scheduling (especially scheduling involving a differential), but even work location when a change in commute time was involved. (Can't remember the specific court case offhand, but I'd be happy to find it if you'd like.
Again, FMLA does consider pay and schedule to be part of an equivalent position.
29 CFR 825.215 specifies that:
(a) An equivalent position is one that is virtually identical to the
employee's former position in terms of pay, benefits and working
conditions, including privileges, perquisites and status. It must
involve the same or substantially similar duties and responsibilities,
which must entail substantially equivalent skill, effort,
responsibility, and authority.
Equivalent pay is addressed specifically in subsection (c):
(c) Equivalent Pay. (1) An employee is entitled to any unconditional
pay increases which may have occurred during the FMLA leave period, such
as cost of living increases. Pay increases conditioned upon seniority,
length of service, or work performed would not have to be granted unless
it is the employer's policy or practice to do so with respect to other
employees on ``leave without pay.'' In such case, any pay increase would
be granted based on the employee's seniority, length of service, work
performed, etc., excluding the period of unpaid FMLA leave.
An employee
is entitled to be restored to a position with the same or equivalent pay
premiums, such as a shift differential. If an employee departed from a
position averaging ten hours of overtime (and corresponding overtime
pay) each week, an employee is ordinarily entitled to such a position on
return from FMLA leave.