Not only did my sim card register without any problems on the Turkish Vodafone network, I also received the usual SMSes containing the tariff info for SMS and data roaming
checking credit and available MBs in roaming worked without any problems.
Unfortunately I chose the 1GB unregistered version of the sim card, so I had no possibility to try it out (no credit). If you'd really like to know I might be able to recharge it and test in in Romania tomorrow.
I'll paste the SMSes I received. (I don't have Google translate to my disposal via my mobile phone now)
Thanks for your offer to help keep the sim alive, I'll keep it in mind