Update - the issue described seems to be related purely to scala worksheets (I tend to use them for playing and prototyping).
I tried described approach, but it fails in my case.
Having Scala 2.10.4 and Jackson libs 2.2.2 the readValuemethod fails on
Jackson libs 2.2.2
com.fasterxml.jackson.databind.JsonMappingException: Argument #0 of constructor [constructor for A$A20$A$A20$Group, annotations: [null]] has no property name annotation; must have name when multiple-paramater constructor annotated as Creator
More details here https://gist.github.com/anonymous/7dc05bfdefe7a9c68d9a. Right now I am trying to find out the correct form of annotations.