  The planned Laser Interferometric Space Antenna (LISA) will be able to detect
gravitational waves (GWs) from intermediate mass binary black holes (IMBBHs) in
the mass range $\sim 10^{2} \mbox{-} 10^{4}\,M_{\odot}$ up to a redshift
$z\sim20$. Modulation effects due to orbital motion of LISA around the Sun
facilitate precise premerger localization of the sources, which in turn would
help in electromagnetic (EM) followups. In this work, we calculate the
uncertainties in sky position, luminosity distance, and time of coalescence as
a function of time to coalescence. For representative masses of the IMBBHs, we
synthesize a population of binaries uniformly located and oriented on a sphere
of radius 3 Gpc and compute the projected parameter measurement uncertainties
using the Fisher information matrix. We find that for systems with a total mass
of $10^3\,M_{\odot}$, the errors in the sky position and luminosity distance
are $\sim 0.4\,\text{deg}^2$ and $\sim 6\%$, respectively, one day prior to
coalescence. The coalescence time can be predicted with an uncertainty
$\lesssim 10$ sec, one day before coalescence. We also find that for
$10^3\,M_{\odot}$, around $40\%$ ($100\%$) of the population has a source
localization that is smaller than the field of view of Athena (LSST) one day
before the merger. These extremely precise measurements can be used to alert
ground-based GW detectors and EM telescopes about the time and location of
these mergers. We also discuss mechanisms that may produce EM emission from
IMBBH mergers and study its detectability using the planned Legacy Survey of
Space and Time (LSST) in the optical and Athena in the x-ray bands. Detection
of an EM transient may provide us vital clues about the environments where
these mergers occur and the distance estimation can pave the way for
cosmography.
