No, actually I don't know. But to be on the safe side I've registered the one SIM card that I've already sold to a fellow forum member on the home network (eplus). On that occassion I've also disabled the voice mailbox as I've described it
here.
By the way you folks might find it interesting that, although not officially documented, AldiTalk can be recharged by bank transfer to the following bank account:
receipient: E-Plus Mobilfunk GmbH & Co.KG
IBAN: DE07 3004 0000 0121 7900 01
BIC: COBADEFFXXX
bank: Commerzbank Düsseldorf
reference: 015751234567 (your Aldi telephone number)
(source:
http://www.prepaid-wiki.de/index.php5/ALDI_TALK)