It's designated as an inbound service number which means you should not be allowed to present it as the CLI number. It should only be assigned as a secondary number. It's not "sharecall" per se. It's a standard rate inbound service number.
Tariffs will, as always, depend on the calling network, but from Telkom it will be no different to calling an 087 number on the same network.
The bigger issue is that of reachability. The one and only number range that I know of on this prefix is 086 999 0000 to 086 999 0999 (1000 numbers) allocated to Nashua Communications.
You may find that these numbers are not YET reachable from all operators as it is a relatively new number range.
Personally, I'd avoid it. Rather use a range that is not designated as "inbound" via the regulator so that you can present it as your caller ID number and, if reachability is important to you, I wouldn't suggest being one of the first to start using a new number prefix that is unfamiliar.
