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On one project I worked on a few years back the customer had a spec sheet for the things telco needed for their equiptment rack that was to be installed on their premise.
One thing our company did was the installation of the ground wire for the rack.
The telco specs basically said a #6 ran to the nearest accessible vertical building steel and terminated with a properly installed crimp connector that got bolted to the steel.
On the rack end they asked for a coil of 10' of wire hanging at the rack.

Maybe a RFI to telco is in order because they sometimes ask for things that an electrician might not think to be necessary or overkill.

I finally stopped laughing at the IT drawings that came in yesterday afternoon long enough to post this.

This just arrived from one of the "I am the IT guy and my word shall not be questioned" people who have NO idea what they're doing.

His drawing contains a table of length and ground wire size:
Less that 13'......#6
13' to 20'.........#4
21' to 26'.........#3
26' to 33'.........#2
33' to 44'.........#1
44' to 52'.........#1/0
52' to 66'.........#2/0
over 66'...........#3/0

This is for a data closet with (4) 15A circuits in a plain vanilla dorky little office building.

Maybe these guys have a lot of stock in one of the copper wire manufacturers??

I just refreshed my memory from the IBM Physical Planning manual. They never asked for more than a #8 and that was to bond an acre or more of non-stringer raised floor.
Usually a #12 was all they wanted
It was also in the bad old days when we were the worst EMI offender with the 400 amp switching power supplies and phase controlled regulators in our big machines. They were very crudely chopping up utility power with largely unfiltered power supplies. Switching transients were everywhere.
I am not sure who the "IT guy" is but he is sadly misinformed

LOL...........................
When the person who gave you that drawing see's the 3/0 after is is installed, do me a favor and get a picture of the look on his face.
Where do these people get this info from?

Find the nearest building steel, drill it for a two-hole compression lug, terminate a #6 AWG and run it above the racks on the cable rack with cable rack "J" hooks. Then tap the #6 AWG ground feeder at each equipment rack with either #6, 8, or 10 with "H" taps and terminate the ground bars using a two-hole compression connector.