The aggregation pipeline builder will allow a $match stage with either an ObjectId('') expression or a $or expression.  However, it will not allow those two to be combined.  Please refer to the attached screenshot.

{
  $or: [
    {'start time': {$gte: ISODate('2016-02-21T11:23:47.000Z')}},
    {'end time': {$gte: ISODate('2016-02-21T11:23:47.000Z')}}
  ],
  _id:ObjectId('572bb8222b288919b68adfa5')
}

In brief testing, combining ObjectId('') with other expressions appears to work.  Combining $or with other expressions appears to work.