Yes, it is. However, instead of using the default {%UnsubscribeLink%} macro expression, we need to compose it manually, according to this example:
<a href="http://domain/cmsmodules/newsletters/cmspages/unsubscribe.aspx?subscriberguid={%SubscriberGUID%}&newsletterguid={%NewsletterGUID%}&issueguid={%IssueGUID%}&contactid={%ContactID%}?query=value&query2=value">Unsubscribe</a>
You may see the link is composed of several parts. Leaving it like this has the same result as the original macro expression. However you can add any number of custom query parameters at the end of the link and provide any additional info about the subscriber. This can be optionally processed in the code-behind of the cmsmodules/newsletters/cmspages/unsubscribe.aspx page.
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