I am not aware that this is possible.

If the extension is a server extension, the extension runs in the context of the user that does the operation that triggers the extension and in the context of his permissions.

The current user would require permissions on Project B to perform the operation there.

Hello, Chidambaram.

I have the similar problem and I am testing a possible solution. I have a extension executing in a project area and I make changes in other project area. After testing other solutions, I find a solution that possibly works. I use a internal server API instead the client API and I don't need the user password for it. You can get the user context in a extension with the "getTeamServiceContext()" method. This method returns a instance of the "com.ibm.team.repository.common.transport.ITeamServiceContext" interface. The "com.ibm.team.repository.service.internal.TeamServiceContext" internal class implements this interface. This internal class contains the current user. You can use the "pushImpersonation" static method in order to replace the current user. Finally you can use the "popImpersonation" static method in order to restore the original user.

public class MyParticipant extends AbstractService implements IOperationParticipant {
    public void run(AdvisableOperation operation, IProcessConfigurationElement participantConfig, IParticipantInfoCollector collector, IProgressMonitor monitor) throws TeamRepositoryException {
                                IContributorHandle contributorHandle = contributorService.fetchContributorByUserId("user.id.in.other.project.area");
                                IContributor contributor = auditableCommon.resolveAuditable(contributorHandle, ItemProfile.CONTRIBUTOR_DEFAULT, monitor);
                                IContributorRecordHandle contributorRecordHandle = contributorService.fetchContributorRecordByUserId(IContributorUserId.FACTORY.create(contributor.getUserId()));
                                IContributorRecord contributorRecord = auditableCommon.resolveAuditable(contributorRecordHandle, ItemProfile.<IContributorRecord> createFullProfile(IContributorRecord.ITEM_TYPE), monitor);
                                UUID[] contributorIdentityUUIDs = new UUID[contributorRecord.getIdentities().size()];
                                List<IContributorIdentity> contributorIdentities = contributorRecord.getIdentities();
                                TeamServiceContext context;

                                for (int i = 0; i < contributorIdentities.size(); i++) {
                                    IContributorIdentity contributorIdentity = contributorIdentities.get(i);

                                    contributorIdentityUUIDs[i] = contributorIdentity.getId();
                                }
                                context = TeamServiceContext.pushImpersonation(contributor.getUserId(), contributor.getItemId(), contributorRecord.getItemId(), contributorIdentityUUIDs);
                                try {
                                ...
                                <you can make changes in the other project area here>
                                ...
                                } finally {
                                    ((TeamServiceContext) getTeamServiceContext()).popImpersonation(context);
                                }

Until now this solution works for me, but I follow to test it because I find this solution recently.