If the internal names of the IK chains are called "RightLeg", or "LeftLeg", they will be set ON by default. To negate this use a different name.

Appears not to be case sensitive. Best to avoid using those names for the internal name also if you want IK's to be off when the figure loads.

A pose file could change the external name but not the internal, so you are down to using a text editor or asking me very nicely to produce a Python script that could do a batch edit. :)