I'm curious: How do you want to calculate the deviation for one single attribute?
Anyway I think you will have to incorporate the script operator to get access to the single components of the formular. The linear regression model is a FormularProvider class, this should give you a good interface to retrieve the coefficients.
If you convert them to a AttributeWeight object, you can apply this to do the multiplication for the whole example set. Might be this is of help depending on how you will answer my question above