Follow up on that 2006 report, Kent sent this 2011 report. This report reviews the ESTI "essential" IPR declarations; the consequences (and privledges) for members as FRAND rates are determined, etc. Note particularly pages 13/14 where IDCC is cited as third with 94 patents. Intense, but interesting data:
An empirical study on the determinants of essential patent claims in compatibility standards
This paper appeared as: Bekkers, R., Bongard, R., & Nuvolari, A. (2011). An empirical study on the
determinants of essential patent claims in compatibility standards. Research Policy, 40, 1001-1015.
http://home.ieis.tue.nl/rbekkers/Bekkers-Bongard-Nuvolari-%282010%29-Essential-patents-%28Author-version2%29.pdf