Catalysis of the reaction: S-adenosyl-L-methionine + trans-aconitate = (E)-3-(methoxycarbonyl)pent-2-enedioate + S-adenosyl-L-homocysteine.
S-adenosyl-L-methionine:(E)-prop-1-ene-1,2,3-tricarboxylate 2\'-O-methyltransferase activity