Prosecutor David Meredith said Bago approached and harassed women who were waiting on the station platform, trying to hug them and asking for drugs.
He would then grope their breasts or crotch before moving on to his next victim.
However, the court heard fresh charges were brought after US authorities located photographs of Voigt and Andrews involved in sex acts with the children.
The photos were passed on to Queensland police who re-interviewed each of the defendants, resulting in new confessions.
She said Allwood would pose a real risk of further offending once released. With time already spent in custody, he will be eligible to apply for parole on July 14.
Allwood pleaded guilty to unlawful stalking in March and the case was adjourned until Friday for his defence to obtain a psychiatric report.
Gordon Anthony Allwood, 42, met a 15-year-old girl and her father in Gatton last January when they arrived to offer assistance to flood victims.
Allwood spent four months stalking the teenager via indecent text messages, following her to work and watching her when she was out.
In March the court heard Allwood told his victim he had an 18-year-old friend named David and pretended to be him in some of the texts.
He also asked for naked photos of her and offered to send her naked photos of himself.