It is not likely that enough recipients will take the effort to report the mail to spamcop.net
There are ways to configure a mail server to automatically report messages that are identified as spam to other blacklists.
Is the spamcop blacklist widely used anyway?
Yes. (I work for a large hosting provider and see it among the most commonly used after Spamhaus.)
At most, some individual Bayesian filters may become more sensitive to the name of the company and travel-related spam, although I'm not sure how hotmail/gmail/yahoo exactly deal with user-reported spam.
Again, some client-side utilities can be configured to automatically report spam to blocklists and spam digesting providers (i.e. pyzor).
The submitter works for a travel agency. Plenty of competition; the chance that the potential customer comes to them is small anyway.
But a lost sale is still a lost sale. If would really suck if one of those would have been a repeat business customer wanting to setup contracts.
I'm afraid that, however unethical this spamming would be, the risk of getting in trouble is rather small.
Again, from someone that works at a large hosting provider, you're right. I think the biggest risk is the potential tarnishing of the business image.
It sounds like the boss is in the knee-jerk reaction. He needs to have a cool head to gently persuade him and show him the business case for not responding. You have to show him that it makes the whole business look unprofessional and the competitor has already done that to themselves. If these are known customers, it would be better to contact them directly via some other means (such as a phone call). You'll do better to work on your customer relationships than you would to respond in such an impersonal and annoying fashion.