Okay Sparky, watch it with that noise. Bottom line is you were played, but they played by the rules. If management felt you were a quality driver that they wanted based on your performance they would have granted you seniority. If in over four months you haven't "proven" yourself to them, then you didn't prove yourself.
Volume is strong for the next month then drops off for a few months (when most newbies get laid
off), so for them to not use you for the next month then bring you on during the slowest time of the year doesn't make sense.
For them to say they'll put you on a harder route if your performance wasn't acceptable on an "easy" route makes no sense. If you didn't get your 30 days before the free period, you didn't get your 30 days. It wasn't an accident that they didn't work you for a couple weeks. This was likely planned in case they didn't like you/your performance.