BBT2000 - ESRI:105602

WKT

VERTCS["BBT2000", 
	DATUM["Brenner_Base_Tunnel_2000", 
		SPHEROID["WGS_1984", 6378137.0, 298.257223563]], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", 1.0], 
	UNIT["Meter", 1.0]]

WKT2

VERTCRS["BBT2000", 
	DATUM["Brenner_Base_Tunnel_2000", 
		ELLIPSOID["WGS_1984", 6378137.0, 298.257223563]], 
	CS[vertical, 1], 
	AXIS["Ellipsoidal height (h)", up, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["Esri", "105602"]]

Data from @esri/proj-codes

{
  "wkid": 105602,
  "latestWkid": 105602,
  "macro": "PE_VCS_BBT2000",
  "name": "BBT2000",
  "wkt": "VERTCS[\"BBT2000\",DATUM[\"Brenner_Base_Tunnel_2000\",SPHEROID[\"WGS_1984\",6378137.0,298.257223563]],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"BBT2000\",DATUM[\"Brenner_Base_Tunnel_2000\",ELLIPSOID[\"WGS_1984\",6378137.0,298.257223563]],CS[vertical,1],AXIS[\"Ellipsoidal height (h)\",up,LENGTHUNIT[\"Meter\",1.0]],ID[\"Esri\",\"105602\"]]",
  "description": "BBT2000",
  "authority": "Esri",
  "version": "13.3.0",
  "deprecated": "no",
  "areaname": "Europe - Brenner",
  "extent": {
    "slat": 46.45,
    "nlat": 47.33,
    "llon": 11.04,
    "rlon": 11.91
  }
}