One of possible way (so far only known to me) how to solve directly and eficiently LP problems with full multi-precision support in MATLAB environment is using of Matlab toolbox for Maple (MTM) by built-in Maple function LPsolve (Optimization package) and multi-precision setup by Maple command "Digits:= 200", for example.
It would be great if the developers of Symbolic Math Toolbox could add in the future some optimization methods!