Does ingestion of alcohol with methylphenidate make it act more like dexmethylphenidate?
Does the ingestion of alcohol, when taking (racemic) methylphenidate can actually make it more potent? 

It is the 2011 study you've mentioned that answers most of the question.

In the study, ethanol co-ingestion with racemic MPH elevated maximal plasma levels of d-MPH by up to 40%. The participants reported greater stimulant effect after alcohol + MPH than after MPH alone (Table 2).

Now, the completely different question is if such combination of alco + MPH is also beneficial and safe.

Also:


  MPH–ethanol coabuse has been widely reported in both annual Drug Abuse
  Warning Network data and the clinical literature.