In the EnvInject plug-in configuration for a job, both the "Keep Jenkins Environment Variables" and "Keep Jenkins Build Variables" check-boxes are selected.

The "Properties Content" section sets the following property:

M2_REPO = ${WORKSPACE}/.repository

However, when a build runs, the log reports:

[EnvInject] - Loading node environment variables.
[EnvInject] - Preparing an environment for the build.
[EnvInject] - Keep Jenkins system variables.
[EnvInject] - Keep Jenkins build variables.
[EnvInject] - Injecting as environment variables the properties content
M2_REPO=${WORKSPACE}/.repository

[EnvInject] - Variables injected successfully.
[EnvInject] - Unset unresolved 'M2_REPO' variable.

and the build operates as if the environment variable is unset. The ${WORKSPACE} property appears to be ignored.