Deutsche Telekom AG has a current market cap of $54 billion USD. The $42.2 B is in Euro.
Tmobile USA is said to contribute about 25% of DT's total income, not valuation. However, we could also try to use the EBITDA valuation, Tmobile/MetroPCS combined ttm EBITDA is about $7.9 Billion, using MetroPCS' current 3.26x market cap/EBITDA multiple, the new company should worth about $25.7 billion. (VZ has a 4.26x and AT&T has a 6.22x MC/EBITDA multiple for comparison's sake)
Personally, I wouldn't use any Sprint's multiple to value the new Tmobile/MetroPCS company, because Sprint hasn't make a dime for so many years.