Hai,
You are correct in saying that the transaction can be also suspended when a method on CMT bean is called (eg, method trans-attribute is NotSupported).
The actual question asks explicitly about BMT beans:
If a transcation is in progress when a method on a BMT bean is called, the transcation is suspended."
and therefore the answer is always 'Yes' - no transaction can propogate into the BMT bean.
Hope it helps

Alex (SCJP 1.4, SCBCD 1.3, SCWCD 1.4, SCJD 1.4)