With materialized view I have set teiid_rel:ON_VDB_START_SCRIPT property for the external matview table. (Simple query to increment a column in table to count invocations.)
Invocation of the script is dependent upon the way the vdb is deployed. The first case (A) doesn't invoke the script, the second (B) does.
A - 1. Copy the vdbname-vdb.xml into deployments folder
2. Start the server
B - 1. Start the server
2. Copy the vdbname-vdb.xml into deployments folder

That means that after server stop (maintenance) the script is not invoked on start, which can cause problems when the script is used to initialize running environment (clear table, create temporary table,...)