Illustration 6.5 on page 64 of the Jaybird manual (http://www.firebirdsql.org/file/documentation/drivers_documentation/Jaybird_2_1_JDBC_driver_manual.pdf) suggests it is possible to configure the transaction mapping through the JDBC URL, as it should be possible to translate that example to the connection URL:

DriverManager.getConnection("jdbc:firebirdsql://localhost/dbalias?TRANSACTION_READ_COMMITTED=isc_tpb_read_committed,isc_no_rec_version,isc_tpb_write,isc_tpb_nowait",
username, password)

However the code in FBDriver and FBDriverPropertyManager shows it only works if the mapping is defined through a Properties object. Configuration through the JDBC url and Properties should be equivalent. It seems to have been broken back in 2004 with the introduction property info, specifically https://github.com/FirebirdSQL/jaybird/commit/d242527af47f2e2a0a97496a020dcc96fe8d7da2