I think what Rene says will work for Bamboo 2.7.

If this is not sufficient for some reason, I think the request for this functionality is captured in BAM-1410, so I will resolve this issue as a duplicate.

Then here Project A would have its own plan with presumably 1 Stage and 1 Job and Project B would depend on it.

OR

Both Projects in the Same plan where Plan A is in 1 Stage and Plan B is in the other stage.

OR

write an additional maven goal to wrap-up your lifecycle if you want to drive it inside your CI.

I do not agree!
Instead of using

mvn clean ; mvn install

I would perfer use the example:

mvn install; mvn deploy

Imagine two projects:

• Parent project
  • Project A
  • Project B depending on A

Now imagine that project B contains some tests that depends on project A and are failing due to a change on project A. If you do (on the parent project)

mvn install ; mvn deploy

The install phase will fail on project B and deploy will not be called.
If you execute

mvn install deploy (or simply mvn deploy)

The project A will be deployed even if project B is failing.

My 5 cents:
As Ulrich noticed there is a technical difference betweeen mvn clean; mvn install and mvn clean install. However a well constructed project shall not be vulnerable to this difference. All Bamboo builds are being build and tested using a mvn clean install command.