The problem is that + is not an allowed character under IDN rules, and it certainly not allowed in the .com TLD. Google most likely will NOT be able to renews that domain under Verisign .com rules.
How was it registered initially if it is prohibited under Verisign rules?
Looks to me like it was purchased initially in 2006, which was before IDNA2008. It currently expires in 2016, and I would suspect that it would be tough to renew that domain when it comes up for renewal, because + (the plus sign) is not allowed in the .com TLD.
I'm not familiar with domain name rules, but it sounds to me like Google has ~5 years to lobby to get the rules changed, or to make +.com so ubiquitous that refusing renewal would be a worse idea than permitting it.