I ran into an issue where I was attempting to load properties for a Spring 3.0 web application in both the application context configuration and the web application configuration.The configuration was initially defined as follows:
Both the application context and the web context referenced the same ‘payment.proxy.X’ placeholders, however, only the placeholders in the application context resolved (ENV_CODE is resolved from the System properties). I found the following quote from Jürgen Höller, one of the founder of Spring, on the spring-dev list from a long time back:
PropertyPlaceholderConfigurer is an implementation of the
BeanFactoryPostProcessor interface: This interface and its sibling
BeanPostProcessor just apply to the BeanFactory that defines them, that is,
to the application context that defines them.If you combine multiple config files into a single contextConfigLocation, a
PropertyPlaceholderConfigurer defined in any of the files will apply to all
of the files, because they are loaded into a single application context.However, a DispatcherServlet has its own application context, just using the
root web application context as parent. Therefore, it needs to define its
own BeanFactoryPostProcessors and/or BeanPostProcessors, in this case its
own PropertyPlaceholderConfigurer.I believe that this is the better general solution: Each application context
might want to resolve its placeholders against its own properties files,
where applying PropertyPlaceholderConfigurer from parent contexts would
interfere.
I then defined the same PropertyPlaceholderConfigurer in both the application context and the web context and the issue resolved.
A Software Guy's Blog 
So you saying that this will not work for following case
You load the PropertyPlaceholderConfigurer context xml at the parentRootContext.
These properties are not available to the application context that are not part of the parentRootContext, in case of multiple context roots.
So if I understand correctly, you are describing a scenario as follows:
If this is the case then yes, the propertyPlaceholder defined in subContext1.xml will not be available in subContext2.xml. If it were instead defined in applicationContext.xml itself, then it should be available in both of the subContext XMLs. I haven’t used Spring in a while (working on a Grails project at the moment) so I am not sure if it has changed, but this was the behavior I observed when I was using it. The applicationContext and the webContext definitely are in separate contexts and will require separately defined propertyPlaceholders.