Hi Gaurav,
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)
Regards,
Vignesh.S