ONE needs to think how a parallel connection is made and how both power sources react to the load.
48 panels into 24 Volts bank means that the panel bank may have a Vmp of at least 68 volts and Voc of around 92+ volts.
The Hydro with 90 Voc may be at the same conditions that the panel and under load the panel or the hydro may set the input voltage as loaded by the MX60, this setting is defined by the internal impedance of both sources, having priority the one with lowest impedance and highest voltage.
So when the MX60 "looks", one with lowest impedance and highest voltage will dominate.
This way one source may feed higher power than the other.
For maximum efficiency the ideal case would be 2 charge controllers to maximize the power fed to the batteries.
By the way, if you have 24 volts bank fed by a 48 Volts panel, it would be best to separate the panels into 2 - 24 volts for emergency purposes in case the charge controller goes bad, paralleling the panels to produce 24 volts feeding directly to the battery bank without a controller ( 2 -24 volts panels in series or 2 - 24 Volts panels in parallel).
Nando