[inquisitor]

Slim's aim to expand globally, especially into Europe, is pretty obvious as he - through AMX - has also built a stake in Telekom Austria (22.76%, currently worth € 0.5 bn) which in addition to Austria operates several cell networks on the Balkans.

While I wouldn't rule out AMX to make a counter bid just to force Telefonica to increase their bid and so withdraw more cash from them, I doubt that E-Plus is that attractive to other bidders that cannot realize such great synergy effects as Telefonica could do (up to an estimated € 5.5 bn). But most importantly E-Plus requires huge investments in its network and in spectrum licenses should it continue to run as a separate network since network quality is subpar and consumer awareness for network quality and bandwidth is growing quickly. The lack of lower frequency spectrum (just a paired 5 MHz block in the 900MHz band which will be reauctioned next year) and especially the lack of fibre network assets (important for backhauling) as well as any fixed-line operations (important for future femto deployment) is a major strategic disadvantage which makes it very difficult for E-Plus to keep pace with the other three players who each own a paired 10MHz-block of LTE800 spectrum and have nationwide fibre networks as well as fixed-line branches.
Against this background I doubt that it would make much sense for AMX to outbid KPN and then invest billions in a saturated, fiercely competitive market with a low pricing level.

Given AT&T's 9% share in AMX (including two board seats) and the fact that AT&T's CEO Randall Stephenson and Carlos Slim are friends I wouldn't expect any interference between these two. But AMX and Telefonica would both be a strategic fit for AT&T who so could become a transamerican carrier.