On second thought I would say "We may well have such scanner devices manufactured by Hewlett Packard, Brother, Xerox, Fujitsu, Canon and perhaps others. Each of them provided the equipment and licensed software to operate the equipment."
Then send out copies to each of those companies legal departments and their sales managers for this equipment.
See if the patent trolls have time to respond to discovery from 5 or 10 lawfirms. Fun!
This is what you call "finding your natural allies".
BTW, I actually do have all that scanner equipment. All different brands too. From Fortune 100 companies with legal departments and outside counsel on retainer. Great fun!
I think this is a pretty easy matter to deal with.
I would write them a letter and CC the scanner vendor's legal department. I'd say "We bought that scanner from Hewlett Packard (just an example), and they provided the software that we use with it. If there is a licensing issue take it up with them. We are their licensee."
If they happened to sue me I'd counter sue Hewlett Packard and bring them in. After all, they put me up to it by selling me the machine and providing that software. If it has to be licensed, they ought to have done that.
It'd just not my problem past that.
Now, if Hewlett Packard was countersued on 300 of these lawsuits they would have to do something, wouldn't they? Or they would be out of business.