I'll start right off by saying I do NOT KNOW! But thinking about it purely as a "simple" mechanical engineering problem, I can't see why not.
First off I'd be prepared for some VERY careful saw work, followed by fine file work (fine needle file probably) for where the X pieces meet. Absolutely NO burrs at all, and most probably very gentle radius-ing to ensure a smooth transition of the nut from the X to Y axis direction (and vice-versa).
Second, I THINK it would be far and away better to make your own special nuts, not use the standard. The nut material to be hard aluminium alloy, and based on the normal square shape but PERHAPS made from material which is a little thicker than the usual for such nuts (less vertical slop in the track, again especially when transitioning for X to Y axis and vice-versa). In addition the conventional square shape of the nut will require very careful SLIGHT radius-ing in both plan and cross-sectional views (fine needle files again) to ensure no binding and very smooth movement, again especially to ensure a smooth transition between axes.
I stress all the above is pure guess work on my part, and if you do try this I imagine you'll need quite a long time with the files to get said smooth transitions between the axes.
I can't think of another method off the top of my head, but just wonder if there isn't a better way altogether than T track to achieve this particular goal?
Above is probably not a lot of help really (lots of, hopefully at least slightly educated, guess work there) but best of luck anyway. I'll be interested to hear how you get on, and/or if someone comes along with a better idea. (There's an idea rumbling around in the back of my mind about using sunken ball bearing drawer runners as linear bearings, but it's not "crystallised" yet, if ever - especially for the X n Y axis transitions)! At it's best I'm just a useless old "CO2 eruption"!
