Selenium Grid error on GitLab CI: Error forwarding the new session Empty pool of VM for setup Capabilities

Since documentation on GitLab CI configuration and Selenium is generally poor, I'm asking for help.

Configuration as by interest point:

gitlab.ci.yml:

image: node:7

variables:
  HUB_PORT_4444_TCP_ADDR: "selenium__hub"
  HUB_PORT_4444_TCP_PORT: "4444"

services:
  - selenium/hub:latest
  - selenium/node-phantomjs:latest

stages:
  - test

test:
  stage: test
  before_script:
    - apt-get update
    - apt-get install -y default-jdk default-jre
    - npm install -s -g @angular/cli@1.0.6
    - npm install -s
    - node ./node_modules/protractor/bin/webdriver-manager update
  script:
    - ./node_modules/.bin/protractor protractor.ci.conf.js

protractor.ci.conf.js:

/*global jasmine */
const { SpecReporter } = require('jasmine-spec-reporter');

exports.config = {
  allScriptsTimeout: 11000,
  specs: [
    './e2e/**/*.e2e-spec.ts'
  ],
  capabilities: {
    'browserName': 'phantomjs',
    'phantomjs.binary.path': './node_modules/phantomjs-prebuilt/bin/phantomjs'
  },
  directConnect: false,
  baseUrl: 'http://localhost:4200/',
  framework: 'jasmine',
  jasmineNodeOpts: {
    showColors: true,
    defaultTimeoutInterval: 30000,
    print: function() {}
  },
  beforeLaunch: function() {
    require('ts-node').register({
      project: 'e2e/tsconfig.e2e.json'
    });
  },
  onPrepare: function() {
    jasmine.getEnv().addReporter(new SpecReporter({ spec: { displayStacktrace: true } }));
  },
  seleniumAddress: 'http://selenium__hub:4444/wd/hub'
};

With the above configuration, GitLab fails with:

$ ./node_modules/.bin/protractor protractor.ci.conf.js
(node:3702) DeprecationWarning: os.tmpDir() is deprecated. Use os.tmpdir() instead.
[09:53:27] I/launcher - Running 1 instances of WebDriver
[09:53:27] I/hosted - Using the selenium server at http://selenium__hub:4444/wd/hub
[09:53:28] E/launcher - Error forwarding the new session Empty pool of VM for setup Capabilities [{phantomjs.binary.path=./node_modules/phantomjs-prebuilt/bin/phantomjs, count=1, browserName=phantomjs}]
[09:53:28] E/launcher - WebDriverError: Error forwarding the new session Empty pool of VM for setup Capabilities [{phantomjs.binary.path=./node_modules/phantomjs-prebuilt/bin/phantomjs, count=1, browserName=phantomjs}]
    at Object.checkLegacyResponse (/builds/netaachen/operator-app/node_modules/selenium-webdriver/lib/error.js:505:15)
    at parseHttpResponse (/builds/netaachen/operator-app/node_modules/selenium-webdriver/lib/http.js:509:13)
    at doSend.then.response (/builds/netaachen/operator-app/node_modules/selenium-webdriver/lib/http.js:440:13)
    at process._tickCallback (internal/process/next_tick.js:109:7)
From: Task: WebDriver.createSession()
    at Function.createSession (/builds/netaachen/operator-app/node_modules/selenium-webdriver/lib/webdriver.js:777:24)
    at createDriver (/builds/netaachen/operator-app/node_modules/selenium-webdriver/index.js:167:33)
    at Builder.build (/builds/netaachen/operator-app/node_modules/selenium-webdriver/index.js:632:14)
    at Hosted.getNewDriver (/builds/netaachen/operator-app/node_modules/protractor/lib/driverProviders/driverProvider.ts:60:29)
    at Runner.createBrowser (/builds/netaachen/operator-app/node_modules/protractor/lib/runner.ts:225:39)
    at q.then.then (/builds/netaachen/operator-app/node_modules/protractor/lib/runner.ts:391:27)
    at _fulfilled (/builds/netaachen/operator-app/node_modules/protractor/node_modules/q/q.js:834:54)
    at self.promiseDispatch.done (/builds/netaachen/operator-app/node_modules/protractor/node_modules/q/q.js:863:30)
    at Promise.promise.promiseDispatch (/builds/netaachen/operator-app/node_modules/protractor/node_modules/q/q.js:796:13)
    at /builds/netaachen/operator-app/node_modules/protractor/node_modules/q/q.js:556:49
[09:53:28] E/launcher - Process exited with error code 199
ERROR: Build failed: exit code 1