I can't rule out that Truphone will just let their numbers run over Vodafone's existing infrastructure but all competitors who have leased such a huge number range before did that to become a so-called full MVNO who establishes its own peering with other operators, which would offer a larger scope technically and financially.
Does anyone happen to have access to the
ITU's mobile network code (MNC) database so he could tell if Truphone has been assigned their own MNC under the German mobile country code (MCC, 262 for Germany)?
If so this would indicate they are intending to become a full MVNO.