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.