Generally software packages include much more import than export filters/functions. The authors usually want to make it simple for you to move to their software, but they have much less to benefit from making it easy to move away from their software. But, I guess, you even asking the above question, means that I’m not telling you anything new here.
WP could actually set a nice precedent and supply an export function for their closest competitor (?!), otherwise, your best course for action would be to ask the MT team or one of their plugin authors for a WP-import function in MT.
