  Intelligent reflecting surfaces (IRSs) were introduced to enhance the
performance of wireless systems. However, from a cellular service provider's
view, a concern with the use of an IRS is its effect on out-of-band (OOB)
quality of service. Specifically, given two operators, say X and Y, providing
services in a geographical area using non-overlapping frequency bands, if
operator-X uses an IRS to optimally enhance the throughput of its users, does
the IRS degrade the performance of operator-Y? We answer this by deriving the
ergodic sum spectral efficiency (SE) of both operators under round-robin
scheduling. We also derive the complementary cumulative distribution function
of the change in effective channel at an OOB user with and without the IRS,
which provides deeper insights into OOB performance. Surprisingly, we find that
even though the IRS is randomly configured from operator-Y's view, the OOB
operator still benefits from the IRS, witnessing a performance enhancement for
free. This happens because the IRS introduces additional paths between the
nodes, increasing the signal power at the receiver and providing diversity
benefits. We verify our findings numerically and conclude that an IRS is
beneficial to every operator, even when the IRS is deployed to optimally serve
only one operator.
