HI Francesco,
I have the same problem with MS Project baselines, PTC.SOFT_ATTRIBUTE_1 is exportet to MS Project but as text with prefix "PARAMETER_NAME|VALUE":
<ExtendedAttribute>
<FieldID>188743731</FieldID>
<Value>Starting|2015-12-25 00:00:00.</Value>
</ExtendedAttribute>
Do you have any suggestion?