Vodafone and 3 Australia: why no network sharing?

Vodafone Australia and 3 Australia are merging into a 50/50 joint venture VHA, apparently to better compete with Telstra and Optus.

Three comments:

• Mobile markets worldwide seem to disagree on the number of players required for just the right amount of competition. In Germany, calls have been heard for years for a merger of the #3 (E-Plus) and #4 (O2) operators to merge. In the Netherlands, the market went from 5 to 3 players, but now the competitive level seems to have dropped below the ideal level; a fourth player could enter once more, once 4G spectrum is auctioned off. France is a comparable case.
  
• Why not do a full network sharing deal, for both passive and active (RAN) elements? Vodafone and 3 would vastly improve their cost base and could still market their own products and services. Vodafone has a solid position in the prepaid market, 3 has more data-centric postpaid subs. The venture is going with the Vodafone brand, so 3 is effectively getting out of the market, in exchange for a 50% share. Migrating 3's subs to Vodafone may cause an incredible headache.
• Are more deals in the making? Rumours have been going around about 3 giving up its position in Italy and the UK. Vodafone comfortably has a position in those countries as well. Australia could be a testing ground for 3 to quietly get out of the mobile business altogether.