You can talk to a Sidekick with ViewProp just like other IED-24 devicew.  You just gotta know the right address.  Below is a list of all mic station related addresses that might be of use:

Base mic station   $7FF0   or  32752

Expansion Board  $7FF1  or  32752

Sidekick #1          $7F01  or  32513

Sidekick #2          $7F02  or  32514

Sidekick #3          $7F03  or  32515

 What you see is for a Sidekick is one object:  528SK Mic Station Manager.  This object contains the same firmware verison information as any other IED-24 products.  The item of interest is the Product Version property.  ViewProp shows the version in decimal.  One should convert to Hex and then interpret the version as if there were periods between the hex nybbles.  See below for a sample screenshot of ViewProp Object Properties.  In this example, the Program Version property is 4160.  This converts to hex 1040 which is then interpreted as  firmware version 1.0.4.0.