Magento – Hide Cash On Delivery Payment even when it is enabled

You can use the event payment_method_is_active.
Create an observer on that and you will get the payment method instance as a parameter.
Check if the customer is logged in deactivate it if it's not.
Something like this:

public function paymentMethodIsActive($observer) {
    $method = $observer->getEvent()->getMehodInstance();
    $result = $observer->getEvent()->getResult();
    if (!$result->isAvailable) { //if the method is not available at all, do nothing
        return $this;
    }
    if ($method->getCode() == 'cashondelivery') { //if method is cache on delivery
        //make it available only if the customer is logged in
        $result->isAvailable = Mage::getSingleton('customer/session')->isLoggedIn();
    }
}

More info about the event observers can be found here

AS i have seen in your reference link you can also see

code for

1) table rates shipping method == flatrate_flatrate

2) cash on delivery" payment method. == cashondelivery

EDIT

class Mage_Shipping_Model_Carrier_Tablerate
    extends Mage_Shipping_Model_Carrier_Abstract
    implements Mage_Shipping_Model_Carrier_Interface
{

    /**
     * code name
     *
     * @var string
     */
    protected $_code = 'tablerate';
}

Simple Magento shipping method code

<pre>Array
(
    [0] => Array
        (
            [value] => Array
                (
                    [0] => Array
                        (
                            [value] => flatrate_flatrate
                            [label] => Fixed
                        )

                )

            [label] => Flat Rate
        )

    [1] => Array
        (
            [value] => Array
                (
                    [0] => Array
                        (
                            [value] => freeshipping_freeshipping
                            [label] => Free
                        )

                )

            [label] => Free Shipping
        )

    [2] => Array
        (
            [value] => Array
                (
                    [0] => Array
                        (
                            [value] => tablerate_bestway
                            [label] => Table Rate
                        )

                )

            [label] => Best Way
        )

    [3] => Array
        (
            [value] => Array
                (
                )

            [label] => Best Way
        )

)

i am sure it will help you.