Yes, it’s true! Apparently, through the fluke of a Death Knight on EJ somehow getting Power Infusioned and realizing that his Frost Strikes only cost 22 RP while under the buff, this discovery was made. Tests were done with various random items, such as Robes of Insight, of which the on-use ability grants 500 mana off the next spell cast in 10 seconds. It also makes Frost Strikes free. Burst of Knowledge, a trinket with a proc that reduces mana cost of spells cast by 100 mana, reduced the cost of Frost Strikes to 22 RP each.
The strange conclusion of this information was the realisation that Spark of Hope, if it worked in the same way as other mana-reduction items and took 4.2 RP off the cost of FS, would be the second-best Frost DPS trinket currently available, behind only the Greatness deck. While this is most likely a bug of some kind, it’s pretty amusing nonetheless. If you can somehow get your hands on a Spark of Hope, let me/EJ know what you find out.
edit: Here’s the EJ post
edit #2: Reports coming in from EJ that Blizzard has gotten their act together and fixed the bug.