Print & Scan differences Snow Leopard vs. Lion?

Question

I have an HP Officejet Pro 8500 (A910a) AiO Printer/Scanner.  It is connected to my network and accessible to many of our home devices including an iMac, a MacBook Pro, iPads and iPhones (via AirPrint).  For the purposes of this topic, I'll refer to it as the HP_8500.  My question is about scanning.
The MacBook Pro runs Snow Leopard 10.6.8.  When I open System Preferences > Print & Scan, it lists the HP_8500 as one of the printers and lists its name, "Open Print Queue...", "Options & Supplies..." etc.  There does not appear to be any way to initiate Scan capabilities from this window.  So I must use either Preview or Image Capture to activate the scanner.
The iMac runs Lion 10.7.1.  When I open System Preferences > Print & Scan, it lists the HP_8500 same as above, except at the top of the window there are two buttons "Print / Scan" at the top of the frame.  So I can easily toggle to Scan to initiate scanning.
Is this in fact a known difference between Snow Leopard and Lion regarding Scanning?  In other words, is there a way to get the Print/Scan button in my Print & Scan window under Snow Leopard or not?  Or is this only available under Lion?
Thanks.

Answer 1

This change was introduced in Lion. For 10.6, the Print & Scan button as seen in Lion would only occur for USB connected AIOs, and only if an ICA driver was present on the Mac. For networked AIOs, there was the ability to add a separate scanner providing a scanner driver was installed on the 10.6 Mac. Here is the view on my 10.6 Mac showing a Canon MP990 AIO and a Canon LiDE 200 standalone scanner, listed under the heading of Scanners.