[inquisitor]

In contrast to German geographical numbers I am not aware of any legal restriction that would hinder Truphone from assigning German mobile numbers to non-residents. Yuilop and sipgate both had products based on German mobile numbers (leased from the now bankrupt MVNO vistream) for months without any regulatory intervention despite they never verified customers' addresses. However yuilop and sipgate were both a thorn in other MNOs' side as they caused assymetrical call flows that converted into cash outflows for competitors (usually the ratio between costs for terminating calls to competitors' networks and the income from inbound calls from competitiors were more or less balanced which those VoIP-services overthrew). Rumour says that vistream's file for bankruptcy was partly caused by Deutsche Telekom who withheld interconnection fee payments to vistream due to suspicions of fraud connected with these innovative services.
Sipgate are currently in the process of becoming their own MVNO, too, (though with a domestic focus) and therefore have also leased a mobile numbering range, +49 1579 from E-Plus, but there seem to be issues in getting networks interconnected, allegedly due to resistance from the other German MNOs who dislike all these new market entrants with their revolutionary business models. I fear Truphone will face similar issues.
So even once Truphone assings German numbers it remains to be seen how reachable they will be.