Most of the time the ” en ” refers to the matter/situation/subject of discussion the news article is discussing about. In this situation I think it’s about the

en = date de lancement de la LTE Advanced dans l’hexagone

But also it’s a common expression assiociated to the alternative of saying

nous n’en parlons pas encore = nous n’en sommes pas encore à évoquer

“En” can be either a pronoun (to replace a nominal group starting with de/du/de la/des) or a preposition (related to place/manner/matter/material).
Here I actually have trouble seeing which one it is (although I’m French :-O).

Anyway, I think it’s idiomatic : en arriver à (quelque chose), en être (quelque part).
Also it’s mostly (average ?) spoken language, I wouldn’t expect that in text.

Litterally it stands for “arriver/être {au point où}/{au moment de}/{prêt à} …”

In your context : “nous ne sommes pas encore prêts à évoquer … “

En is a complicated word. In this form, it is a pronoun with no antecedent, which is a bit of a strange concept (I think some grammars classify it as a particle, i.e. a word that doesn’t fall into any neat classification). This happens in a number of idioms.

En être à means “to have reached the stage when”.

Nous n’en sommes pas encore à évoquer une quelconque date de lancement de la LTE Advanced dans l’hexagone.
We have not reached the point where we might discuss a launch date for LTE Advanced in France.

Où en êtes-vous ? — J’en ai fait la moitié.
How far have you got? — I’ve processed half of them.