If you want just the package names you could use helper classes to query from a Configuration. And so your query would be
(MTProject
newFromVersion: (ConfigurationOfAthens project version: #development)
inConfiguration: ConfigurationOfAthens) dependenciesFilteredBy: MTPackage.
These MT classes - which sounds like they should belong to Metacello - are not in Metacello package, but currently in Versionner (included by default in Pharo images).
Diving into results reveals that some "MTPackages" has not their corresponding "RPackage" (this could be a bug, or some weird feature in the package representation models). So you would need further filtering:
((MTProject
newFromVersion: (ConfigurationOfAthens project version: #development)
inConfiguration: ConfigurationOfAthens) dependenciesFilteredBy: MTPackage)
select: [ :pkgName |
(RPackageOrganizer default
packageNamed: pkgName name asSymbol
ifAbsent: []) notNil ]