I figured it out. Following goes in web.config for IIS
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<rewrite>
<rules>
<!--# Media Vault Rewrite Rules-->
<rule name="In Protected Directory" stopProcessing="true">
<match url="^wp-content/uploads(/_mediavault/.*\.\w+)$" ignoreCase="false" />
<action type="Rewrite" url="index.php?mgjp_mv_file={R:1}" appendQueryString="true" />
</rule>
<rule name="In Standard Media Directory" stopProcessing="true">
<match url="^wp-content/uploads(/.*\.\w+)$" ignoreCase="false" />
<conditions>
<add input="{QUERY_STRING}" pattern="^(?:.*&)?mgjp_mv_download=safeforce(?:&.*)?$" ignoreCase="false" />
</conditions>
<action type="Rewrite" url="index.php?mgjp_mv_file={R:1}" appendQueryString="true" />
</rule>
<!-- Usual WordPress Rule works if before Media Vault, but Vault won't setup initially -->
<rule name="wordpress" patternSyntax="Wildcard">
<match url="*"/>
<conditions>
<add input="{REQUEST_FILENAME}" matchType="IsFile" negate="true"/>
<add input="{REQUEST_FILENAME}" matchType="IsDirectory" negate="true"/>
</conditions>
<action type="Rewrite" url="index.php"/>
</rule>
</rules>
</rewrite>
</system.webServer>
</configuration>