It is a Police issue, as long as leeds are in this league we will play them Midweeks. Their are numerous police issues as to why it must be a midweek game.... If it was a weekend it would be guaranteed that either Manure or Citeh will be at home that weekend not to mention the other surrounding clubs therefore police numbers could cause an issue! Take into account that Oldham Town Centre on Saturday nights isnt the safest place in the world add 4-5k of leeds scum to that = chaos. With the attendance likely to be high there needs to be a full police presence, plus the trouble at previous tics/leeds matches all combined means it will be a mid - week game! If i remember correctly when we played leeds in the Premiership the home leg was also midweek and had a bit of crowd trouble (dont hold me to that as i was only a nipper) . Oldham Athletic & Oldham Police when sending off their fixture requirements always ask for this match to be midweek!
Have a look on the fishul site, the news article on how fixtures are produced gives a better insight!