[Babcock_Hall]

Unlikely probably just means slow.  Also, in this reaction the primary carbocation rearranges to a tertiary carbocation.  Whether the rearrangement itself causes the overall reaction to speed up or not, relative to a reaction without a rearrangement, is not a question that I can answer.

[RedsAreRaw]

All right. Well thanks for the help Babcock_Hall.

[wildfyr]

The rate determining step is the group leaving, that carbocation rearrangement is extremely fast