Companies the size of Marvel are always involved in litigation of some kind. If they gave in to every request for a subpoena or deposition, their legal team would never have time for anything else.
If we want to stay on the parking ticket comparison, it's standard procedure for all companies involved in transportation and delivery to contest parking tickets because they get so many and it costs nothing to fight them. I should know, writing those letters was one of my first jobs.
Ryan is the one who has to be worried about the Marvel subpoena. By all accounts, they were uncharacteristically hands-off with the Deadpool/Wolverine production and largely let Ryan and Shawn Levy run the show. If it turns out that Ryan was making decisions that connect the Marvel brand, however tangentially, to a high-profile lawsuit that there is no reason for them to have anything to do with, they may not be so accommodating the next time Ryan wants to visit the Deadpool well.