As far i know in the On Demand 9r1 Environments will Send email only to Supplier (Participants) who are all Invited for that particular Event.
With an information saying Buyer Organization invites you to participate in the Even with Status of the Event New,Pending Selection,award
Alternatively Sourcing Administrator can send a message to Supplier from the Message Board without shooting a mail.
About Capable of sending alert or advise to certain people that a bid is ready to be opened- Is not possible On Premise (I don't have idea on Demand System)
The functionality you are seeking is not available in the event at this time. If you are using a full project, you could create a notification task to notify team members of the opening of the bid, but that would not be actually tied to the event. That means if you extend your event, the task would not automatically extend also.