There are 2 different perspectives on this, TMs and UDRPs. A UDRP can be fought because the TM holder cannot prove bad faith registration. The only way they could lose it if it was proven they used the domain in bad faith (IE- changed their site to sell widgets which was TMed). Now from the TM side, I am less familiar with it, but I believe the TM holder can challenge on the grounds of the TM through the court of law.
It is tricky, but just hope Business B goes the UDRP route because it is easier to defend with teh given senario...
I do not believe a trademark has any power over a business that was using the mark the same way before the TM was granted. The older business is grandfathered.
Where it gets interesting is when the old business moves into new areas. If you were good at predicting, lets see...Say you thought the future of computing was via ESP. You trademark ibm as a company researching ESP oh, inter-brain mental or something. Then in a few years when IBM (big) wants to start marketing their new brain to computer system there you are in the way.
They would just run over you, but you get the idea...
A very interesting precedent has just been set with the 'cheaptickets' domains.
As I understand it, the owner of the .com (who had TM'd 'cheaptickets') was going after the owner of the .ca version, in a WIPO challenge.
The .ca owner, deciding to fight fire with fire, countered by applying to have the TM taken away from the .com owner, on grounds of it being a generic term.
The .ca owner won, and the TM has been revoked...
I guess what youre really asking is what B can and cant do? They can pretty.
Much do what they want, but how to enforce their claims is their problem.
Trademark infringement is an inherent risk when registering a domain name. If.
Someone claims your domain name is infringing their trademark, its up to you.
To decide whether to fight it or not.
There's no simple answer without having all available facts. One outcome does.
Not necessarily say how another will turn out.
If you're after some sort of specifics, specific conditions and/or questions are.
In that scenario Business A wins period. TM works from date of first use...
You are generally asking the same type of question answered here daily except in an odd way.
Business B has no right to Business A. Business A as a matter of fact could go after Business A.
Apple Computer and Apple Records are a good realworld example. And when Apple Computer delved into the online music world it treaded onto the Apple Records territory. Lawsuits were the result and I am not even sure if they were settled or are just awaiting trial. There is a thread around here somewhere about it...