T-Mobile CEO John Legere has been party crashing this week at CES. Now his company looks ready to crash early termination fees with its “Uncarrier 4.0” announcement.t-mobile uncarrier at&t ces

A leaked T-Mobile ad has surfaced, all but confirming the carrier’s plans to pay off ETFs for families that switch to T-Mobile and trade in their devices. The ad also notes that purchase of a qualified T-Mobile plan and device is required when porting over up to five numbers from AT&T, Verizon or Sprint.

Invites for the event went out before Christmas as rumors circulated suggesting that T-Mobile was preparing to offer up to $350 per line to families willing to switch.

Last week, AT&T appeared to launch a preemptive response when it announced up to $450 in credits for customers willing to switch from AT&T to T-Mobile. AT&T confirmed the deal is targeted at only T-Mobile customers.

Legere directed a response on Twitter to AT&T CEO Randall Stephenson before pulling off a bit of viral marketing by crashing and getting kicked out of AT&T’s CES party.

Meanwhile, both T-Mobile and AT&T have been strengthening their spectrum portfolios ahead of the carriers’ impending war. T-Mobile Monday bought 700 MHz A-Block licenses from Verizon for $2.4 billion, as well as some AWS and PCS licenses. AT&T bought 49 AWS licenses from Aloha Partners.

Now it’s almost time for T-Mobile to launch its official response and possibly go after ETFs, one of the big remaining pain points for mobile customers. The T-Mobile Uncarrier 4.0 event begins at 12:30 p.m. PT today and is being webcast.