Boston property manager always wins work. Should association have more control?

Our property manager has a parent company that does work (of all kinds) through out the properties they manage painting, shoveling, deck replacing, patio repairing etc. While the people do do a good job we should be establishing relationships with other vendors. Capitol work done by his company the Property Manager gets 10% as the management supervisor. When asked to secure bids for any work the PM company submits a bid always lower than everyone else and more or less begs for the job. Since it's cheaper the board usually agrees.  Although the bids are sealed his is always lower than the others. I wonder if the board could have one set of bids sent to the chair and if his parent company intended to bid on the job he should inform the board in advance. I think it's healthy to establish other relationships. not sure his parent company would be bidding on jobs if he was no longer the Property Manager.  Boston MA.