The Warriors are buoyant at present after inflicting a first RDS Arena defeat in 29 against European champions Leinster - the Scottish side's first RaboDirect Pro12 victory of the season.
And Lineen believes there will be no signs of No. 8 Beattie sulking over his World Cup snub on Friday.
"It's great to have Johnnie back in the fold," said Lineen. "He's a talented, confident player who has been a great asset for Glasgow Warriors for a long time, and I've been very impressed with how he's dealt with not being part of the Rugby World Cup.
"He was obviously extremely disappointed not to be selected, but I'd be more worried about a player who didn't initially react that way because it would hint at a lack of ambition.
"The great thing about Johnnie is that he quickly moved on from that disappointment and threw himself into getting back fit and performing for Glasgow Warriors.
"We've got good competition in the back row at the moment, with the likes of Rob Harley, Chris Fusaro, Ryan Wilson, James Eddie and Rory Pitman all showing up well.
"Friday night will be another learning curve for these players, and having shown they can live with a side like Leinster, it's about us as a team proving ourselves all over again."
63x46.png){kind=logo}