Yes, there is documentation and as far as I know there is no secrecy.
You will find it on this webpage [4]. Look for "1401 Programming Support". After installation (works fine in wine, too), you can find these interfaces:
~/.wine/drive_c/1401Lang/WinSupp/Use1401.h ~/.wine/drive_c/1401Lang/WinSupp/Use1432.dll
Seems to me your best bet would be to ignore the drivers completely and work on a winelib replacement for Use1432.dll. There shouldn't be any need to run or replace the device driver, as long as the applications you need go through that dll rather than accessing it directly (and both of those options are likely more difficult than replacing a dll).
You can use the winedump command to generate a .spec file which you can then use to build a stub dll. See http://www.winehq.org/docs/winelib-guide/bindlls for some information on that. In this case, your interface is dictated to you by the header and dll file, and the corresponding Linux api probably consists of opening a Linux device file and doing ioctl() calls on it.
Note that you don't need to implement all or even any functions to use the dll. If a program calls an unimplemented function, the function name will be sent to stderr, and the program will crash. Which is a good way to check whether your programs are using the dll, and which functions you'll need. As you implement them, remember to replace the "stub" lines in your spec file with stdcall lines so they are actually used.
Also, if you want to distribute your code, keep in mind there's no license on their header, and you may need to replace it if you don't want a dependency on it.
BTW, try1432.exe doesn't appear to use use1432.dll and instead attempts to directly access the device file at \.\CED1. I tested this by running with WINEDEBUG=+loaddll.