classes.php

<?php

interface TemplatingAware
{
    function setTemplating(EngineInterface $engine);
}

interface RouterAware
{
    function setRouter(RouterInterface $router);
}

class AbstractController implements TemplatingAware, RouterAware
{
    protected $engine;
    protected $router;

    public function setTemplating(EngineInterface $engine)
    {
        $this->engine = $engine;
    }

    public function setRouter(RouterInterface $router)
    {
        $this->router = $router;
    }
}

class SomeController extends AbstractController
{
    ///some code
}

class SomeOtherController extends AbstractController
{
    ///some code
}

services.xml

<interface class="TemplatingAware">
    <call method="setTemplating">
        <argument type="service" id="templating" />
    </call>
</interface>
<interface class="RouterAware">
    <call method="setRouter">
        <argument type="service" id="router" />
    </call>
</interface>
<service id="some.controller" class="SomeController" />
<service id="some.other.controller" class="SomeOtherController" />

now SomeController and SomeOtherController will have $engine and $router properties populated with correct services

Shouldn't public function setRouter(Router $router) type hint on the interface? public function setRouter(RouterInterface $router) ?

oh, yeah, let me fix that, thanks

Имхо не самый удачный пример. Почему бы не сделать просто interface ContainerAware и

class AbstractController implements ContainerAware
{
  protected function getTemplating()
  {
    return $this->container->get('templating');
  }
}

You're free to use whatever you want. This is to show how you could achieve less configuration for controllers as services using interface injection.
Keep in mind that no matter how many controllers you have registered in DIC, as long as they extend this base AbstractController class, they will all get templating and routing without a single line of extra configuration.
What you're showing is just a different way of getting services in controller, and is not relevant to this example