This isn't entirely the case, however I can't provide too many details because it is not our systems that we are talking about. The information you have is not inaccurate, but it does not fully reflect the situation.
In these cases I have sympathy with BT, where an exchange reaches capacity there is an awful lot of work to do to install extra stuff. The "card" you talk about is a notional thing which reflects all manner of routers, terminating equipment, interconencts and the like.
BT outsource much of their hardware installation in many areas of their business to third parties. This is logical as people like Fujitsu, Marconi and Alcatel manufactuer the kit - It is VERY complicated stuff and in these cases manufacture and install go hand in hand.
With regard to capacity planning, there is no doubt that the recent popularity of ADSL has taken everyone by surprise. BT's job is made much harder by the postcode marketting of some of the major ISP's who flood certain areas with connections, but won't tell BT where or when they are doing it. This is also a problem with Friaco and often explains why people suddenly start experiancing problems on dialup exchanges.
BT and their partners are upgrading exchanges as fast as they can. Again, the work required at some exchanges is pretty immense and some of the lenghts thay have gone to have actually been remarkable. We do have issues with some of the things BT do with regard to ADSL, but i this case I don't think anyone is to blame.
The good news is that it looks like your exchange is being upgraded as we speak, hopefully the installation will be able to take place in just a few days.