don't know that it would even need to be mandatory......if it were freely available and I were in the field, I'd take advantage of it.  However if reading writing on the wall, I'd look to get tight or sell and look for new ventures.......RB seemed proactive.

Sir Richard Branson cuts his stake in Virgin Media     ..... 15 May 2009
http://www.telegraph.co.uk/finance/newsbysect...Media.html

Virgin Media sold for £10bn      .....06 Feb 2013
http://www.itv.com/news/story/2013-02-06/us-c...-for-10bn/

John Malone another B-naire steps up.....not sure what RB is up to.

.....the dates were of interest to me when considering dutv timeline.  Don't claim to know anything for fact, just thinking out loud a little......thought folks more knowing than I would chime in and help sort out most likely scenario.