At least for me, the problem is not in the double backslashes from "wine c:\\windows\\etc", but in the un-quoted last parameter (the .lnk file) and it's (single) escaping backslashes.
would turn into this:
env WINEPREFIX="/home/sb/.wine" wine C:\\windows\\command\\start.exe /Unix "/home/sb/.wine/dosdevices/c:/users/sb/Start Menu/Programs/Microsoft Office/Microsoft Office Word 2007.lnk"
At least for me, the problem is not in the double backslashes from "wine c:\\windows\\etc", but in the un-quoted last parameter (the .lnk file) and it's (single) escaping backslashes.
So a workaround can be, using this example:
env WINEPREFIX= "/home/ sb/.wine" wine C:\\windows\ \command\ \start. exe /Unix /home/sb/ .wine/dosdevice s/c:/users/ sb/Start\ Menu/Programs/ Microsoft\ Office/Microsoft\ Office\ Word\ 2007.lnk
would turn into this: "/home/ sb/.wine" wine C:\\windows\ \command\ \start. exe /Unix "/home/ sb/.wine/ dosdevices/ c:/users/ sb/Start Menu/Programs/ Microsoft Office/Microsoft Office Word 2007.lnk"
env WINEPREFIX=