You'd have to jump through a couple of hurdles, but you'd, in essence, use the "stringread" command to extract the byte that represents the tile you're moving into, the "hextodec" command to convert it to a number, then some simple tests in BASIC to determine if that number belongs to a tile that you can/cannot move into.
Beyond that and manually having to do what a matrix does internally, there's really no difference between using binary strings for the string tilemapper and using a matrix-based one found with xLIB.
