I have modified my deprecated positional parameter HQL queries to the following JPA-style positional parameter:

Query query = sessionFactory.getCurrentSession().createQuery("from Customer where name = ?0");
query.setParameter(0, "Smith");

The second line now leads to an Exception:

Exception in thread "..." org.hibernate.QueryParameterException: Position beyond number of declared ordinal parameters. Remember that ordinal parameters are 1-based! Position: 1
	at org.hibernate.engine.query.spi.ParameterMetadata.getOrdinalParameterDescriptor(ParameterMetadata.java:80)
	at org.hibernate.engine.query.spi.ParameterMetadata.getOrdinalParameterExpectedType(ParameterMetadata.java:86)
	at org.hibernate.internal.AbstractQueryImpl.determineType(AbstractQueryImpl.java:450)
	at org.hibernate.internal.AbstractQueryImpl.setParameter(AbstractQueryImpl.java:422)

Debugging the parsing of the query in HqlSqlBaseWalker, the code executes line https://github.com/hibernate/hibernate-orm/blob/4.2.7.SP1/hibernate-core/src/main/antlr/hql-sql.g#L754 which is described by:
An ejb3-style "positional parameter", which we handle internally as a named-param
So here a named parameter is created.
But above Exception in ParameterMetadata is due to searching for an ordinal/positional parameter which is obviously not there, as it was saved a a named parameter before. In the debugger I can see my parameter in the namedDescriptorMap, being of type NamedParameterDescriptor.