I'm in a similar boat to you, in that I have no control over the setup / backup of my databases except by contacting the person who admins our "enterprise" backup software. Thankfully I could tell them what sort of schedules to set, but I'm trying to get the backups under my control, at least for the databases.
As for your infrastructure managers concerns, you can further reduce the potential risk footprint from ransomware by having the AD team create and deploy a GPO to block the execution of Internet Explorer / Edge / Firefox / Chrome / etc on servers. We have such a policy here in place and frankly, it's not as big an inconvenience as you might expect.
I would also suggest tossing this link to your IM as well, to help explain *why* you want to control the database backups:
https://spaghettidba.com/2017/09/13/expensive-enterprise-backup-tools-a-survival-guide/
Some of it, he'll probably look at and scoff at. Some of it, though, might make him think more about giving you said control. But most important, work *with* him, rather than standing firm on what you want. Not being able to easily restore prod to QA / Dev environments? Work with him on that, maybe get an extra share that you can run a "one-off" backup to from production that QA / Dev can read from, that is not used for anything else (and possibly even with a policy or scheduled task to empty out said location daily.)
But, also, as Steve said, be careful about putting production data in dev environments.
Thanks! The link is great, this is exactly what I have been struggling with. Data Domain and HP StoreOnce have the ability to create a share off the applicance. The share leverages the dedup of the appliance. This way you can use native tools to write backups. This is what I am proposing. I just feel as if the implementation of the share is overly restrictive.