Firstly, if Waldronate posts then take his word over mine but heres my best guess.

FT can export a binary file which is a grid of values. FT has the option of what type of values it exports as either signed 16bit integers (shorts) or floats. When its export the width in samples is entered and I believe that this is not saved as part of the data so you need to know the value.

The guess part is what happens on import because I don't use or own FT but I expect that it will ask for the bin filename and also the number of samples width and the type of data that the bin file relates to - or there is a master terrain type file which references the bin file and contains this extra data for you.

Its a long shot that you could get another program to export your terrain into this format directly so you will probably need to use an in between program or program it yourself. I suspect that going via a grayscale image would be easiest tho.

Have you looked at Wilbur too ? If there is a program that could export to this format then thats the one to look at first.