I've met several people - usually 'bar-braggers' - who've claimed that either they, or the company they work for, have some special type of software which can get round withheld caller IDs. Despite this, I've never heard of anyone who can actually prove that it can be done!
Dialling 141 before a number doesn't stop the caller's number being forwarded to the exchange. (If it did, the phone company wouldn't know where to send the bill!). What it does, however, is to instruct the computer at the exchange not to forward the caller's number to the recipient of the call.
The theory behind these claims about 'magic software' states that it's possible for the call recipient to send a code back to the computer at the exchange which instructs it to forward the caller ID. There seems to be no proof that such a technique is possible. Those call recipients who have a legitimate reason to have all caller IDs disclosed to them (principally the emergency services) simply have an agreement with the telephone companies that all caller IDs will be forwarded. (i.e. they don't need, or use, any special software).
As I've stated, it's almost certain that the type of software you refer to is entirely mythical. If it's not, the phone company would be in breach of the Data Protection Act for failing to maintain the privacy of its customers. Also, the company using the software would be in breach of the Telecommunications Act (and possibly the Misuse of Computers Act) for using such software.
Chris