I don't think it exists any more; if it does, it'll probably be based around the SFT(X) taskbook. If you don't need it, I wouldn't bother - speak to your RA about teh kind of thing that your board like to see and concentrate on that!!
The BEC does still exist - well it did in Jul 2006 when I completed mine, and I've not seen any DIN or RNTM etc saying it no longer exists.
The BEC is a pre-requisite for SUY selection for anyone who is a candidate for mainstream warfare branch. I don't think it is based around SFT(X) taskbook as SUY(X) officers carry out SFT(X) however it does satisfy the requirements of STCW by ensuring SUY(X) are at a similar level as their direct entry colleagues by the time they are on SFT.
The BEC is awarded by a CO on completion of the bridge experience taskbook and is valid for 3 years. The taskbook covers amongst other things, navigation and shiphandling and includes some ops room time (20 hours if I remember). It requires a minimum of 300 (50 percent coastal) hours as 2OOW and you must also take the Fleet RoR exams and achieve a mark in excess of 80 percent.
MNRN - Are you an SUY candidate? If you are Warfare and a candidate for deep specialist I would recommend that you go for your BEC if you are in a unit which will allow it. It will show committment and will also give you another option for commission depending on vacancies in your specialist branch compared to mainstream.
I'm fully familiar with this process so feel free to ask any questions.