How Dynamics CRM Ribbon changes are merged from multiple solutions -

we have 2 development teams working on seperate modules of dynamics crm in different solutions, team develops customizations in solution a, exports managed solution a, managed solution imported on team b's dynamics development organization on regular basis, team b develops customizations in unmanaged solution b , exports managed solution when given customer.

when ready customer can either import managed solution or managed solution b on top of managed solution a.

but both solution , solution b includes changes ribbons. wondering how these changes merged. because in above scenario team a's managed solution imported development environment of team b. @ point team b might have unmanaged changes ribbon well.

i wondering how dynamics crm merges these changes. , wondering if there can case changes in solution can overwritten solution b. though mutually exclusive.

from deduce customizations.xml, when import managed solution, don't see ribbon changes related solution in customizations.xml more when export unmanaged solution contains application ribbon. makes me think when import managed solution, changes in managed solution merged application ribbon.

any information appreciated.

as far i've researched, entity ribbon changes shipped along entities , merged automatically. global application ribbon , custom group changes shipped under client extensions in solution, far i've researched automatically merged when managed solutions imported 1 after another.