I have tried open partition encrypted via truecrypt using 'options="--type tcrypt"' but it failed. dmcrypt initscript detects partition is luks (isLuks returns false) and uses plain mode: 'cryptsetup create' that ignores '--type' option. It looks like there is no command 'cryptsetup isTcrypt'.
Please add support for 'open --type tcrypt'.
Please also take into account that 'cryptsetup open --type tcrypt' always prompt for passphrase even if device is encrypted via keyfile only and password is not required. Maybe initscript should use 'echo -e "" | cryptsetup open ...' for such case?