Recently, I have found 'another' method to find MIN number from a RUIM card. If Nokia handset is not available or a smartphone.
I have just used an unlocked MTS dongle EC122, which I use for laptop internet.
Just insert your RUIM Card in this dongle & software Mobile Partner will start automatically.
then, in settings you can select diagnostic, where few parameters related to RUIM card will be visible. Like sms numbers etc.
Here you will find an IMSI number. which is ia 15 digit number. Last 10 digits are actaully MIN number associated with this RUIM card.
I have checked with another smartphone user & my own RUIM card, (whos number, I transfered to my HTC Rhyme, by entering MIN number found from this method).
Guru's please, correct if this is not the case always !!