Depending on your need for this my suggestion would be to use HICommandCLI and run it against any system you are interested in getting the volume information from.

Getting data from HiCommandCLi is a pain, but it works with the correct formats and output manipulation. I would also look into Command Director and see if you can pull information from there.

HiCommandCLI doesn't show the usable capacity available, but instead shows the total size and the consumed size, so you would need to extract that info from there. I am no expert, but for example running ./HiCommandCLI.sh getstoragearray subtarget=LDEV will give you a lot of data about all volumes in Command Suite.

Attached is a tiny python script I wrote that calls the HiCommandCLI commands formats a bit and then displays the info in a more readable fashion. Maybe it can give you some ideas.